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Full vulnerability report · 2026
CVE-2026-55040High confidence

Microsoft SharePoint Weak Authentication Vulnerability

Microsoft · SharePoint

9.1CriticalCVSS 3.1
Recommended action
Patch now

CISA confirms exploitation in the wild and lists 2026-08-21 as the remediation due date.

Patch available
R
Operational reassessment

Published severity in operational context

Open reassessment dashboard →
Published severityCriticalOperational priority:Critical, unchanged from published severity.unchanged

Evidence used

  • CISA confirms exploitation in the wild.
  • A structured source references public exploit or proof-of-concept material.
  • The selected CVSS metric records a network-reachable, unauthenticated path with no user interaction.
  • EPSS is 69.54% for the current model date.

Compensating controls

  • Validate the affected product branch and deploy the verified fixed release.
  • Restrict the affected network interface to trusted sources where business-safe.
  • Increase monitoring for the attack path and post-exploitation behaviour described in the report.

Verification

  1. Confirm that the asset runs Microsoft SharePoint and falls inside the recorded affected range.
  2. Verify the installed build against the product-specific fixed version after deployment.
  3. Validate exposure, authentication requirements and compensating controls in the actual environment.
  4. Reopen this reassessment when CVSS, KEV, EPSS, exploit evidence or remediation changes.
Mitigation target: Within 3 daysRemediation target: Within 90 days

This automated reassessment organises public evidence. It does not know asset exposure, business impact or control effectiveness and does not replace CVSS or a human risk decision.

Optional official sources

National CERT insights
?CERT means Computer Emergency Response Team; CSIRT is the closely related term Computer Security Incident Response Team.

Choose official national sources for this report. Each advisory shows its original language. Your selection is remembered on this device and included in shared links.

Official European source

ENISA European Vulnerability Database

Official EUVD identifiers, advisory evidence and known-exploited context. Missing fields are not treated as evidence of low risk.

1 current
ENISA EUVD identifier

EUVD-2026-44211

CISA KEV mirrored by ENISA

Weak authentication in Microsoft Office SharePoint allows an unauthorized attacker to bypass a security feature over a network.

EUVD state
Present in the current official mapping
Known exploitation
Recorded by ENISA since 18 Aug 2026. Evidence sources: cisa_kev.
ENISA score
9.1 · CVSS 3.1
Advisory evidence
3 linked advisory records
Explicit mitigation evidence

Only statements that explicitly mention a fix, patch, update, workaround or mitigation are shown here.

  • csaf_ncscnl · NCSC-2026-0237Kwetsbaarheden verholpen in Microsoft Office
Recommended actionPatch now

CISA confirms exploitation in the wild and lists 2026-08-21 as the remediation due date.

Patch available
01

What, why and how

Microsoft SharePoint contains a weak authentication vulnerability which allows an unauthorized attacker to bypass a security feature over a network.

What

Microsoft SharePoint contains a weak authentication vulnerability which allows an unauthorized attacker to bypass a security feature over a network.

Why

The product uses an authentication mechanism to restrict access to specific users or identities, but the mechanism does not sufficiently prove that the claimed identity is correct.

How

An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.

What

Microsoft SharePoint contains a weak authentication vulnerability which allows an unauthorized attacker to bypass a security feature over a network.

Why

The product uses an authentication mechanism to restrict access to specific users or identities, but the mechanism does not sufficiently prove that the claimed identity is correct.

How

An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.

02

Exploit reality and attack path

CVSS severity, EPSS forecast probability, public exploit material and CISA-confirmed exploitation are separate signals.

Observed exploitation
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
Confirmed in the wild

CISA added this CVE to its Known Exploited Vulnerabilities catalogue on 2026-08-18.

Public PoC / exploit material
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
Reference recorded

A structured CVE source labels at least one public reference as exploit material. BlackTree has not independently validated that it is safe, reliable or weaponised.

Likely attack path
a network path → Weak Authentication → cause the confidentiality, integrity or availability impact described by the vendor
Attack surface
Network
Privileges required
None: unauthenticated exploitation is possible
User interaction
None
Attack complexity
Low: no specialised conditions are recorded
Security boundary
Unchanged: impact remains within the vulnerable component's security authority
Weakness
?CWE means Common Weakness Enumeration: a standard category for the underlying weakness.
CWE-1390 ↗

CWE-1390: Weak Authentication. The product uses an authentication mechanism to restrict access to specific users or identities, but the mechanism does not sufficiently prove that the claimed identity is correct.

CVSS vector
?CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N/E:U/RL:O/RC:C

Common Vulnerability Scoring System 3.1: the compact vector below is decoded into plain language.

AVNetworkAttack vector: The vulnerable component can be reached over a network.ACLowAttack complexity: No specialised conditions are required beyond attacker-controlled input.PRNonePrivileges required: The attacker does not need an account or existing privileges.UINoneUser interaction: No action by another user is required.SUnchangedScope: The security impact remains within the vulnerable component's authority.CHighConfidentiality impact: A successful attack can cause a major loss.IHighIntegrity impact: A successful attack can cause a major loss.ANoneAvailability impact: No direct loss is represented by this metric.
Post-exploitation / living off the land
No specific living-off-the-land technique is confirmed in the structured sources. Monitor normal administration tools for activity inconsistent with the affected service's baseline.
NetworkUnauthenticatedCWE-1390CISA KEVPublic exploit reference
A

Official authority intelligence

Only matched European and national findings are included. Language selectors and unavailable sources are omitted.

ENISA EUVD · EUVD-2026-44211Known-exploited evidence recorded

Weak authentication in Microsoft Office SharePoint allows an unauthorized attacker to bypass a security feature over a network.

Official EUVD record ↗
BSI · German · WID-SEC-2026-2317Microsoft Office Produkte: Mehrere Schwachstellen

Ein Angreifer kann mehrere Schwachstellen in verschiedenen Microsoft Office Produkten ausnutzen, um beliebigen Programmcode auszuführen, um Informationen offenzulegen, um falsche Informationen darzustellen, um seine Privilegien zu erhöhen, und um Sicherheitsvorkehrungen zu umgehen.

Official advisory ↗
Canadian Centre for Cyber Security · English · AV26-804Microsoft security advisory – August 2026 monthly rollup (AV26-804) – Update 4

As of August 11, 2026, Microsoft is affected by vulnerabilities in the following products: On August 18, 2026, Cybersecurity and Infrastructure Security Agency (CISA) added CVE-2026-33824 and CVE-2026-55040 to their Known Exploited Vulnerabilities (KEV) Database.

Official advisory ↗
Canadian Centre for Cyber Security · English · AL26-017AL26-017 - Critical vulnerabilities impacting Microsoft SharePoint Server – CVE-2026-56164, CVE-2026-55040 and CVE-2026-58644

An Alert is used to raise awareness of a recently identified cyber threat that may impact cyber information assets, and to provide additional detection and mitigation advice to recipients. The Canadian Centre for Cyber Security (Cyber Centre) is also available to provide additional assistance regarding the content of this Alert upon request.

Official advisory ↗
CERT-FR · French · CERTFR-2026-AVI-0872Multiples vulnérabilités dans les produits Microsoft

CVE-2026-55023 du 14 juillet 2026 Bulletin de sécurité Microsoft CVE-2026-55026 du 14 juillet 2026 Bulletin de sécurité Microsoft CVE-2026-55027 du 14 juillet 2026 Bulletin de sécurité Microsoft CVE-2026-55028 du 14 juillet 2026 Bulletin de sécurité Microsoft CVE-2026-55030 du 14 juillet 2026 Bulletin de sécurité Microsoft CVE-2026-55032 du 14 juillet 2026 Bulletin de sécurité Microsoft CVE-2026-55033 du 14 juillet 2026 Bulletin de sécurité Microsoft CVE-2026-55034 du 14 juillet 2026 Bulletin de sécurité Microsoft CVE-2026-55035 du 14 juillet 2026 Bulletin de sécurité Microsoft CVE-2026-55038 du 14 juillet 2026 Bulletin de sécurité Microsoft CVE-2026-55040 du 14 juillet 2026 Bulletin de sécurité Microsoft CVE-2026-55045 du 14 juillet 2026 Bulletin de sécurité Microsoft CVE-2026-55047 du 14 juillet 2026 Bulletin de sécurité Microsoft CVE-2026-55050 du 14 juillet 2026 Bulletin de sécurité Microsoft CVE-2026-55051 du 14 juillet 2026 Bulletin de sécurité Microsoft CVE-2026-55052 du 14 juillet 2026 Bulletin de sécurité Microsoft CVE-2026-55055 du 14 juillet 2026 Bulletin de sécurité Microsoft CVE-2026-55121 du 14 juillet 2026 Bulletin de sécurité Microsoft CVE-2026-55124 du 14 juillet 2026 Bulletin de sécurité Microsoft CVE-2026-55125 du 14 juillet 2026 Bulletin de sécurité Microsoft CVE-2026-55126

Official advisory ↗
CSIRT Italia · Italian · aggiornamenti-mensili-microsoft-22Aggiornamenti Mensili Microsoft

nuova finestra - - CVE-2026-55054 : apre una nuova finestra - - CVE-2026-55053 : apre una nuova finestra - - CVE-2026-55052 : apre una nuova finestra - - CVE-2026-55051 : apre una nuova finestra - - CVE-2026-55050 : apre una nuova finestra - - CVE-2026-55049 : apre una nuova finestra - - CVE-2026-55048 : apre una nuova finestra - - CVE-2026-55047 : apre una nuova finestra - - CVE-2026-55046 : apre una nuova finestra - - CVE-2026-55045 : apre una nuova finestra - - CVE-2026-55044 : apre una nuova finestra - - CVE-2026-55043 : apre una nuova finestra - - CVE-2026-55042 : apre una nuova finestra - - CVE-2026-55041 : apre una nuova finestra - - CVE-2026-55040 : apre una nuova finestra - Presente CVE-2026-55039 : apre una nuova finestra - - CVE-2026-55038 : apre una nuova finestra - - CVE-2026-55037 : apre una nuova finestra - - CVE-2026-55036 : apre una nuova finestra - - CVE-2026-55035 : apre una nuova finestra - - CVE-2026-55034 : apre una nuova finestra - - CVE-2026-55033 : apre una nuova finestra - - CVE-2026-55032 : apre una nuova finestra - - CVE-2026-55031 : apre una nuova finestra - - CVE-2026-55030 : apre una nuova finestra - - CVE-2026-55029 : apre una nuova finestra - - CVE-2026-55028 : apre una nuova finestra - - CVE-2026-55027 : apre una nuova finestra - - CVE-2026-55026 : apre una n

Official advisory ↗
JVN iPedia · Japanese · JVNDB-2026-023951マイクロソフトのMicrosoft SharePoint Serverにおける弱い認証に関する脆弱性

Microsoft Office SharePointの認証の弱さにより、未承認の攻撃者がネットワーク経由でセキュリティ機能を回避できる可能性があります。

Official advisory ↗
KISA KrCERT/CC · Korean · KNVD-6915美 CISA 발표 주요 Exploit 정보공유(Update. 2026-08-18)

Microsoft SharePoint Weak Authentication Vulnerability

Official advisory ↗
KISA KrCERT/CC · Korean · KNVD-6882MS 7월 보안 위협에 따른 정기 보안 업데이트 권고

crosoft PowerPoint 원격 코드 실행 취약성 | | Microsoft Office OneNote | CVE-2026-55133 | Microsoft OneNote 원격 코드 실행 취약성 | | Microsoft Office PowerPoint | CVE-2026-55043 | Microsoft PowerPoint 원격 코드 실행 취약성 | | Microsoft Office | CVE-2026-55139 | Microsoft Office 정보 유출 취약성 | | Microsoft Office | CVE-2026-55042 | Microsoft Office 정보 유출 취약성 | | Microsoft Office Word | CVE-2026-55130 | Microsoft Word 원격 코드 실행 취약성 | | Microsoft Office Word | CVE-2026-55128 | Microsoft Word 원격 코드 실행 취약성 | | Microsoft Office | CVE-2026-55140 | Microsoft Office 원격 코드 실행 취약성 | | Microsoft Office Word | CVE-2026-55142 | Microsoft Word 정보 유출 취약성 | | Microsoft Office SharePoint | CVE-2026-55040 | Microsoft SharePoint Server 보안 기능 바이패스 취약성 | | Microsoft Office | CVE-2026-55056 | Microsoft Office 원격 코드 실행 취약성 | | Microsoft Office Word | CVE-2026-55134 | Microsoft Word 원격 코드 실행 취약성 | | Microsoft Office SharePoint | CVE-2026-55051 | Microsoft SharePoint Server 정보 유출 취약성 | | Microsoft Office SharePoint | CVE-2026-55126 | Microsoft SharePoint Server 스푸핑 취약성 | | Microsoft Office Excel | CVE-2026-55131 | Microsoft Excel 원격 코드 실행 취약성 | | Microsoft Office | CVE-2026-55057 | Microsoft Office 정보 유출 취약성 | | Microsoft Office Excel | CVE-2026-55122 | Microsoft Excel 정보 유출 취약성 | | Microsoft Office Excel | CVE-2026-55053 | Microsoft Excel 원격 코드 실행

Official advisory ↗
NCSC-NL · Dutch · NCSC-2026-0237Kwetsbaarheden verholpen in Microsoft Office

Een kwaadwillende kan de kwetsbaarheden misbruiken om aanvallen uit te voeren die kunnen leiden tot categorieën schade, zoals benoemd in onderstaande tabel. Voor succesvol misbruik moet de kwaadwillende het slachtoffer misleiden een malafide bestand te openen of link te volgen, met uitzondering van SharePoint. Voor succesvol misbruik van kwetsbaarheden in SharePoint is geen gebruikersinteractie nodig, anders dan het volgen van een malafide link. Microsoft heeft in een update bevestigd dat SharePoint kwetsbaarheid CVE-2026-58644 actief als zeroday is misbruikt. Het NCSC raadt aan kwetsbare SharePoint systemen zo snel mogelijk te updaten naar de nieuwste versie om misbruik te voorkomen. De kwetsbaarheid CVE-2026-58644 betreft een deserialization-kwetsbaarheid welke misbruik zou kunnen worden om op afstand code uit te voeren. Mogelijk is de kwetsbaarheid CVE-2026-58644 in combinatie met SharePoint-kwetsbaarheid CVE-2026-56164 door kwaadwillende te misbruiken om zonder authenticatie op afstand code uit te voeren. De kwetsbaarheid CVE-2026-56164 betreft een privilegeescalation-kwetsbaarheid, deze zou misbruikt kunnen worden om rechten binnen een netwerk te verhogen. UPDATE: Volgens watchTowr is er een publieke exploit code voor SharePoint kwetsbaarheid CVE-2026-50522 gepubliceerd en wordt deze op on-premise versies van SharePoint nu ook actief misbruikt. Kwaadwillenden kunnen deze kwetsbaarheid misbruiken om zichzelf voor langere termijn toegang tot netwerken van kwetsbare systemen te verschaffen, door middel van het stelen van machine-keys. ``` Microsoft Office SharePoint: |----------------|------|-------------------------------------| | CVE-ID | CVSS | Impact | |----------------|------|-------------------------------------| | CVE-2026-54108 | 6.50 | Voordoen als andere gebruiker | | CVE-2026-56164 | 5.30 | Verkrijgen van verhoogde rechten | | CVE-2026-50522 | 9.80 | Uitvoeren van willekeurige code | | CVE-2026-58644 | 9.80 | Uitvoeren van willekeurige code | | CVE-2026-55016 | 4.60 | Voordoen als andere gebruiker | | CVE-2026-55019 | 4.60 | Voordoen als andere gebruiker | | CVE-2026-55020 | 4.60 | Voordoen als andere gebruiker | | CVE-2026-55021 | 7.30 | Voordoen als andere gebruiker | | CVE-2026-55030 | 4.60 | Voordoen als andere gebruiker | | CVE-2026-55034 | 7.30 | Voordoen als andere gebruiker | | CVE-2026-55126 | 7.30 | Voordoen als andere gebruiker | | CVE-2026-55051 | 6.50 | Toegang tot gevoelige gegevens | | CVE-2026-55040 | 9.10 | Omzeilen van beveiligingsmaatregel | | CVE-2026-55052 | 8.80 | Verkrijgen van verhoogde rechten | | CVE-2026-55135 | 4.60 | Voordoen als andere gebruiker | | CVE-2026-56157 | 5.40 | Voordoen als andere gebruiker | | CVE-2026-58277 | 8.80 | Verkrijgen van verhoogde rechten | |----------------|------|-------------------------------------| Microsoft Office Word: |----------------|------|-------------------------------------| | CVE-ID | CVSS | Impact | |----------------|------|-------------------------------------| | CVE-2026-55050 | 5.50 | Toegang tot gevoelige gegevens | | CVE-2026-55032 | 7.80 | Uitvoeren van willekeurige code | | CVE-2026-55033 | 7.80 | Uitvoeren van willekeurige code | | CVE-2026-55124 | 5.50 | Uitvoeren van willekeurige code | | CVE-2026-55127 | 7.80 | Uitvoeren van willekeurige code | | CVE-2026-55055 | 7.80 | Uitvoeren van willekeurige code | | CVE-2026-55038 | 7.80 | Uitvoeren van willekeurige code | | CVE-2026-55132 | 7.80 | Uitvoeren van willekeurige code | | CVE-2026-55134 | 7.80 | Uitvoeren van willekeurige code | | CVE-2026-55142 | 5.50 | Toegang tot gevoelige gegevens | | CVE-2026-55128 | 7.80 | Uitvoeren van willekeurige code | | CVE-2026-55130 | 7.80 | Uitvoeren van willekeurige code | |----------------|------|-------------------------------------| Microsoft Office PowerPoint: |----------------|------|-------------------------------------| | CVE-ID | CVSS | Impact | |----------------|------|-------------------------------------| | CVE-2026-55043 | 7.80 | Uitvoeren van willekeurige code | | CVE-2026-55123 | 7.80 | Uitvoeren van willekeurige code | | CVE-2026-55120 | 7.80 | Uitvoeren van willekeurige code | |----------------|------|-------------------------------------| Microsoft Office: |----------------|------|-------------------------------------| | CVE-ID | CVSS | Impact | |----------------|------|-------------------------------------| | CVE-2026-56193 | 7.10 | Toegang tot gevoelige gegevens | | CVE-2026-47290 | 7.80 | Uitvoeren van willekeurige code | | CVE-2026-50301 | 7.80 | Uitvoeren van willekeurige code | | CVE-2026-50314 | 7.80 | Uitvoeren van willekeurige code | | CVE-2026-50467 | 7.80 | Uitvoeren van willekeurige code | | CVE-2026-55017 | 7.80 | Uitvoeren van willekeurige code | | CVE-2026-55018 | 7.80 | Uitvoeren van willekeurige code | | CVE-2026-55022 | 7.80 | Uitvoeren van willekeurige code | | CVE-2026-55023 | 5.50 | Toegang tot gevoelige gegevens | | CVE-2026-55125 | 7.80 | Uitvoeren van willekeurige code | | CVE-2026-55026 | 6.20 | Toegang tot gevoelige gegevens | | CVE-2026-55027 | 5.50 | Toegang tot gevoelige gegevens | | CVE-2026-55028 | 5.50 | Toegang tot gevoelige gegevens | | CVE-2026-55047 | 5.50 | Toegang tot gevoelige gegevens | | CVE-2026-55045 | 8.40 | Uitvoeren van willekeurige code | | CVE-2026-55049 | 7.80 | Uitvoeren van willekeurige code | | CVE-2026-55129 | 7.80 | Uitvoeren van willekeurige code | | CVE-2026-55035 | 5.50 | Toegang tot gevoelige gegevens | | CVE-2026-55057 | 5.50 | Toegang tot gevoelige gegevens | | CVE-2026-55056 | 7.80 | Uitvoeren van willekeurige code | | CVE-2026-55140 | 7.80 | Uitvoeren van willekeurige code | | CVE-2026-55042 | 5.50 | Toegang tot gevoelige gegevens | | CVE-2026-55139 | 5.50 | Toegang tot gevoelige gegevens | | CVE-2026-50665 | 7.80 | Toegang tot gevoelige gegevens | | CVE-2026-56192 | 5.50 | Toegang tot gevoelige gegevens | | CVE-2026-56195 | 5.50 | Toegang tot gevoelige gegevens | |----------------|------|-------------------------------------| Microsoft Office OneNote: |----------------|------|-------------------------------------| | CVE-ID | CVSS | Impact | |----------------|------|-------------------------------------| | CVE-2026-55133 | 7.80 | Uitvoeren van willekeurige code | |----------------|------|-------------------------------------| Microsoft Office Excel: |----------------|------|-------------------------------------| | CVE-ID | CVSS | Impact | |----------------|------|-------------------------------------| | CVE-2026-50675 | 7.80 | Uitvoeren van willekeurige code | | CVE-2026-50678 | 6.60 | Toegang tot gevoelige gegevens | | CVE-2026-54988 | 6.10 | Toegang tot gevoelige gegevens | | CVE-2026-55899 | 7.80 | Uitvoeren van willekeurige code | | CVE-2026-55948 | 7.80 | Uitvoeren van willekeurige code | | CVE-2026-58618 | 7.80 | Uitvoeren van willekeurige code | | CVE-2026-47642 | 7.80 | Uitvoeren van willekeurige code | | CVE-2026-48580 | 5.50 | Toegang tot gevoelige gegevens | | CVE-2026-55024 | 7.80 | Uitvoeren van willekeurige code | | CVE-2026-50408 | 5.50 | Toegang tot gevoelige gegevens | | CVE-2026-55046 | 5.50 | Toegang tot gevoelige gegevens | | CVE-2026-55025 | 7.80 | Uitvoeren van willekeurige code | | CVE-2026-55031 | 7.80 | Uitvoeren van willekeurige code | | CVE-2026-55048 | 7.80 | Uitvoeren van willekeurige code | | CVE-2026-55029 | 7.80 | Uitvoeren van willekeurige code | | CVE-2026-55039 | 7.80 | Uitvoeren van willekeurige code | | CVE-2026-55041 | 7.80 | Uitvoeren van willekeurige code | | CVE-2026-55138 | 5.50 | Toegang tot gevoelige gegevens | | CVE-2026-55136 | 7.80 | Uitvoeren van willekeurige code | | CVE-2026-55141 | 7.80 | Uitvoeren van willekeurige code | | CVE-2026-55036 | 7.80 | Uitvoeren van willekeurige code | | CVE-2026-55044 | 7.80 | Uitvoeren van willekeurige code | | CVE-2026-55054 | 6.50 | Toegang tot gevoelige gegevens | | CVE-2026-55037 | 7.80 | Uitvoeren van willekeurige code | | CVE-2026-55058 | 7.80 | Uitvoeren van willekeurige code | | CVE-2026-55137 | 7.80 | Uitvoeren van willekeurige code | | CVE-2026-55053 | 7.80 | Uitvoeren van willekeurige code | | CVE-2026-55122 | 7.10 | Toegang tot gevoelige gegevens | | CVE-2026-55131 | 7.80 | Uitvoeren van willekeurige code | | CVE-2026-54131 | 7.80 | Uitvoeren van willekeurige code | | CVE-2026-55898 | 6.10 | Toegang tot gevoelige gegevens | | CVE-2026-55947 | 7.80 | Uitvoeren van willekeurige code | | CVE-2026-55949 | 7.80 | Uitvoeren van willekeurige code | | CVE-2026-56156 | 7.80 | Uitvoeren van willekeurige code | |----------------|------|-------------------------------------| Windows GDI: |----------------|------|-------------------------------------| | CVE-ID | CVSS | Impact | |----------------|------|-------------------------------------| | CVE-2026-50387 | 7.80 | Verkrijgen van verhoogde rechten | |----------------|------|-------------------------------------| ```

Official advisory ↗
03

Patch and workaround

Operational remediation based on structured source evidence.

Status
?Patch availability is based on structured fixed-version fields and authoritative update references. If no fix is verified, check the vendor advisory before making a change.
Patch available
Affected
Fixed
The Cyber Centre recommends that organizations upgrade affected Microsoft SharePoint instances to a fixed version: Affected product Affected versions Fixed versions Microsoft SharePoint Enterprise Server 2016 16.0.0 before 16.0.5561.1001 16.0.5561.1001 Microsoft SharePoint Server 2019 16.0.0 before 16.0.10417.20175 16.0.10417.20175 Microsoft SharePoint Server Subscription Edition 16.0.0 before 16.0.19725.20434 16.0.19725.20434 The Cyber Centre recommends organizations: Identify all on-premises SharePoint Server instances, particularly those exposed to the internet Use or upgrade to supported versions of on-premises Microsoft SharePoint Server Apply the latest security updates from Microsoft to all affected SharePoint Servers including (Subscription Edition, 2019, and 2016) Monitor SharePoint servers for suspicious activity, including unusual requests, web shells, malicious processes, unauthorized access attempts, and machine key theft indicators Harden SharePoint Deployments: Enable Antimalware Scan Interface (AMSI) integration for SharePoint web applications Configure AMSI Request Body Scan Mode to Full Mode where operationally feasible Restrict or eliminate direct Internet exposure of SharePoint servers whenever possible Limit access to SharePoint Central Administration and management interfaces Monitor for Indicators of Compromise: Organizations should closely monitor SharePoint environments for: Unexpected privilege escalation activity Unauthorized authentication attempts Suspicious IIS machine key access Evidence of deserialization attacks or web shell deployment Microsoft Defender and AMSI detections related to SharePoint exploitation activity Important note: Microsoft SharePoint Enterprise Server 2016 Footnote 11 and Server 2019 Footnote 12 are end of life  as of  July 14, 2026 . Organizations are urged to migrate to a supported version. In addition, the Cyber Centre strongly recommends that organizations review and implement the Cyber Centre's Top 10 IT Security Actions with an emphasis on the following topics Footnote 13 . Patch operating systems and applications Harden operating systems and applications Isolate web-facing applications Should activity matching the content of this alert be discovered, recipients are encouraged to report via My Cyber Portal or email contact@cyber.gc.ca .
Action
Apply the fixed release for the affected product branch as recorded by Canadian Centre for Cyber Security. Validate the exact product and build in the linked advisory before deployment.
Workaround
No verified workaround is recorded. If business-safe, reduce exposure to the affected interface and allow only trusted sources until authoritative guidance is available.
04

Evidence and provenance

Published 14 Jul 2026 · Last source change 25 Sept 2026, 18:24 UTC · CWE-1390 · Weak Authentication

CVE recordCVE.org · 5.2
CVSS sourceCNA
EPSS source
?The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.
FIRST · tracked since 2026-08-14
European sourceENISA EUVD · EUVD-2026-44211
Product sourceCISA KEV
Remediation sourceCVE/CNA references
CWE sourceOther authority
NVD statusNVD enriched

Core structured fields are present and their contributing authorities are shown above.

Material change intelligence

What changed after publication

View recent updates ↗
  1. Vendor guidanceAuthoritative vendor guidance changed: added remediation: msrc.microsoft.com/CVE-2026-55040; removed remediation: cyber.gc.ca/al26-017-critical-vulnerabilities-impacting-microsoft-sharepoint-server-cve-2026-56164-cve-2026-55040-cve-2026-58644.
    Before
    patch: msrc.microsoft.com/CVE-2026-55040 · remediation: cyber.gc.ca/al26-017-critical-vulnerabilities-impacting-microsoft-sharepoint-server-cve-2026-56164-cve-2026-55040-cve-2026-58644
    After
    patch: msrc.microsoft.com/CVE-2026-55040 · remediation: msrc.microsoft.com/CVE-2026-55040
    secure@microsoft.com ↗
  2. Affected versionsThe structured affected or fixed version information changed.
    Before
    Microsoft SharePoint Enterprise Server 2016: 16.0.0 < 16.0.5561.1001; Microsoft SharePoint Server 2019: 16.0.0 < 16.0.10417.20175; Microsoft SharePoint Server Subscription Edition: 16.0.0 < 16.0.19725.20434 · Fixed: The Cyber Centre recommends that organizations upgrade affected Microsoft SharePoint instances to a fixed version: Affected product Affected versions Fixed versions Microsoft SharePoint Enterprise Server 2016 16.0.0 before 16.0.5561.1001 16.0.5561.1001 Microsoft SharePoint Server 2019 16.0.0 before 16.0.10417.20175 16.0.10417.20175 Microsoft SharePoint Server Subscription Edition 16.0.0 before 16.0.19725.20434 16.0.19725.20434 The Cyber Centre recommends organizations: Identify all on-premises SharePoint Server instances, particularly those exposed to the internet Use or upgrade to supported versions of on-premises Microsoft SharePoint Server Apply the latest security updates from Microsoft to all affected SharePoint Servers including (Subscription Edition, 2019, and 2016) Monitor SharePoint servers for suspicious activity, including unusual requests, web shells, malicious processes, unauthorized access attempts, and machine key theft indicators Harden SharePoint Deployments: Enable Antimalware Scan Interface (AMSI) integration for SharePoint web applications Configure AMSI Request Body Scan Mode to Full Mode where operationally feasible Restrict or eliminate direct Internet exposure of SharePoint servers whenever possible Limit access to SharePoint Central Administration and management interfaces Monitor for Indicators of Compromise: Organizations should closely monitor SharePoint environments for: Unexpected privilege escalation activity Unauthorized authentication attempts Suspicious IIS machine key access Evidence of deserialization attacks or web shell deployment Microsoft Defender and AMSI detections related to SharePoint exploitation activity Important note: Microsoft SharePoint Enterprise Server 2016 Footnote 11 and Server 2019 Footnote 12 are end of life as of July 14, 2026 . Organizations are urged to migrate to a supported version. In addition, the Cyber Centre strongly recommends that organizations review and implement the Cyber Centre's Top 10 IT Security Actions with an emphasis on the following topics Footnote 13 . Patch operating systems and applications Harden operating systems and applications Isolate web-facing applications Should activity matching the content of this alert be discovered, recipients are encouraged to report via My Cyber Portal or email contact@cyber.gc.ca .
    After
    Microsoft SharePoint Enterprise Server 2016: 16.0.0 < 16.0.5561.1001; Microsoft SharePoint Server 2019: 16.0.0 < 16.0.10417.20175; Microsoft SharePoint Server Subscription Edition: 16.0.0 < 16.0.19725.20434 · Fixed: An authoritative update reference is available, but the fixed version is not recorded in the structured CVE fields. Check the linked vendor advisory for the applicable release.
    CISA KEV ↗
  3. Vendor guidanceAuthoritative vendor guidance changed: added remediation: msrc.microsoft.com/CVE-2026-55040; removed remediation: cyber.gc.ca/al26-017-critical-vulnerabilities-impacting-microsoft-sharepoint-server-cve-2026-56164-cve-2026-55040-cve-2026-58644.
    Before
    patch: msrc.microsoft.com/CVE-2026-55040 · remediation: cyber.gc.ca/al26-017-critical-vulnerabilities-impacting-microsoft-sharepoint-server-cve-2026-56164-cve-2026-55040-cve-2026-58644
    After
    patch: msrc.microsoft.com/CVE-2026-55040 · remediation: msrc.microsoft.com/CVE-2026-55040
    secure@microsoft.com ↗
  4. Affected versionsThe structured affected or fixed version information changed.
    Before
    Microsoft SharePoint Enterprise Server 2016: 16.0.0 < 16.0.5561.1001; Microsoft SharePoint Server 2019: 16.0.0 < 16.0.10417.20175; Microsoft SharePoint Server Subscription Edition: 16.0.0 < 16.0.19725.20434 · Fixed: The Cyber Centre recommends that organizations upgrade affected Microsoft SharePoint instances to a fixed version: Affected product Affected versions Fixed versions Microsoft SharePoint Enterprise Server 2016 16.0.0 before 16.0.5561.1001 16.0.5561.1001 Microsoft SharePoint Server 2019 16.0.0 before 16.0.10417.20175 16.0.10417.20175 Microsoft SharePoint Server Subscription Edition 16.0.0 before 16.0.19725.20434 16.0.19725.20434 The Cyber Centre recommends organizations: Identify all on-premises SharePoint Server instances, particularly those exposed to the internet Use or upgrade to supported versions of on-premises Microsoft SharePoint Server Apply the latest security updates from Microsoft to all affected SharePoint Servers including (Subscription Edition, 2019, and 2016) Monitor SharePoint servers for suspicious activity, including unusual requests, web shells, malicious processes, unauthorized access attempts, and machine key theft indicators Harden SharePoint Deployments: Enable Antimalware Scan Interface (AMSI) integration for SharePoint web applications Configure AMSI Request Body Scan Mode to Full Mode where operationally feasible Restrict or eliminate direct Internet exposure of SharePoint servers whenever possible Limit access to SharePoint Central Administration and management interfaces Monitor for Indicators of Compromise: Organizations should closely monitor SharePoint environments for: Unexpected privilege escalation activity Unauthorized authentication attempts Suspicious IIS machine key access Evidence of deserialization attacks or web shell deployment Microsoft Defender and AMSI detections related to SharePoint exploitation activity Important note: Microsoft SharePoint Enterprise Server 2016 Footnote 11 and Server 2019 Footnote 12 are end of life as of July 14, 2026 . Organizations are urged to migrate to a supported version. In addition, the Cyber Centre strongly recommends that organizations review and implement the Cyber Centre's Top 10 IT Security Actions with an emphasis on the following topics Footnote 13 . Patch operating systems and applications Harden operating systems and applications Isolate web-facing applications Should activity matching the content of this alert be discovered, recipients are encouraged to report via My Cyber Portal or email contact@cyber.gc.ca .
    After
    Microsoft SharePoint Enterprise Server 2016: 16.0.0 < 16.0.5561.1001; Microsoft SharePoint Server 2019: 16.0.0 < 16.0.10417.20175; Microsoft SharePoint Server Subscription Edition: 16.0.0 < 16.0.19725.20434 · Fixed: An authoritative update reference is available, but the fixed version is not recorded in the structured CVE fields. Check the linked vendor advisory for the applicable release.
    CISA KEV ↗
  5. Affected versionsThe structured affected or fixed version information changed.
    Before
    16.0.0 < 16.0.5561.1001; 16.0.0 < 16.0.10417.20175; 16.0.0 < 16.0.19725.20434 · Fixed: An authoritative update reference is available, but the fixed version is not recorded in the structured CVE fields. Check the linked vendor advisory for the applicable release.
    After
    Microsoft SharePoint Enterprise Server 2016: 16.0.0 < 16.0.5561.1001; Microsoft SharePoint Server 2019: 16.0.0 < 16.0.10417.20175; Microsoft SharePoint Server Subscription Edition: 16.0.0 < 16.0.19725.20434 · Fixed: An authoritative update reference is available, but the fixed version is not recorded in the structured CVE fields. Check the linked vendor advisory for the applicable release.
    CNA ↗
  6. Public exploit evidencePublic exploit evidence changed from No public exploit to Public exploit reference.
    Before
    No public exploit
    After
    Public exploit reference
    github.com ↗
  7. Public exploit evidencePublic exploit evidence changed from Public exploit reference to No public exploit.
    Before
    Public exploit reference
    After
    No public exploit
    CVE.org ↗
  8. CISA KEV stateCISA KEV now confirms exploitation in the wild.
    Before
    not listed in CISA KEV
    After
    listed in CISA KEV since 2026-08-18
    CISA KEV ↗
  9. Affected versionsThe structured affected or fixed version information changed.
    Before
    Microsoft SharePoint Enterprise Server 2016: 16.0.0 < 16.0.5561.1001; Microsoft SharePoint Server 2019: 16.0.0 < 16.0.10417.20175; Microsoft SharePoint Server Subscription Edition: 16.0.0 < 16.0.19725.20434 · Fixed: An authoritative update reference is available, but the fixed version is not recorded in the structured CVE fields. Check the linked vendor advisory for the applicable release.
    After
    Microsoft SharePoint Enterprise Server 2016: 16.0.0 < 16.0.5561.1001; Microsoft SharePoint Server 2019: 16.0.0 < 16.0.10417.20175; Microsoft SharePoint Server Subscription Edition: 16.0.0 < 16.0.19725.20434 · Fixed: The Cyber Centre recommends that organizations upgrade affected Microsoft SharePoint instances to a fixed version: Affected product Affected versions Fixed versions Microsoft SharePoint Enterprise Server 2016 16.0.0 before 16.0.5561.1001 16.0.5561.1001 Microsoft SharePoint Server 2019 16.0.0 before 16.0.10417.20175 16.0.10417.20175 Microsoft SharePoint Server Subscription Edition 16.0.0 before 16.0.19725.20434 16.0.19725.20434 The Cyber Centre recommends organizations: Identify all on-premises SharePoint Server instances, particularly those exposed to the internet Use or upgrade to supported versions of on-premises Microsoft SharePoint Server Apply the latest security updates from Microsoft to all affected SharePoint Servers including (Subscription Edition, 2019, and 2016) Monitor SharePoint servers for suspicious activity, including unusual requests, web shells, malicious processes, unauthorized access attempts, and machine key theft indicators Harden SharePoint Deployments: Enable Antimalware Scan Interface (AMSI) integration for SharePoint web applications Configure AMSI Request Body Scan Mode to Full Mode where operationally feasible Restrict or eliminate direct Internet exposure of SharePoint servers whenever possible Limit access to SharePoint Central Administration and management interfaces Monitor for Indicators of Compromise: Organizations should closely monitor SharePoint environments for: Unexpected privilege escalation activity Unauthorized authentication attempts Suspicious IIS machine key access Evidence of deserialization attacks or web shell deployment Microsoft Defender and AMSI detections related to SharePoint exploitation activity Important note: Microsoft SharePoint Enterprise Server 2016 Footnote 11 and Server 2019 Footnote 12 are end of life as of July 14, 2026 . Organizations are urged to migrate to a supported version. In addition, the Cyber Centre strongly recommends that organizations review and implement the Cyber Centre's Top 10 IT Security Actions with an emphasis on the following topics Footnote 13 . Patch operating systems and applications Harden operating systems and applications Isolate web-facing applications Should activity matching the content of this alert be discovered, recipients are encouraged to report via My Cyber Portal or email contact@cyber.gc.ca .
    Canadian Centre for Cyber Security ↗
Material fields only · duplicate refreshes suppressed · history retained for the configured operational retention period
CVE published
Added to CISA KEV
Fixed release or patch reference recorded
Fixed release recorded from official guidance
ENISA EUVD · EUVD-2026-44211↗Canadian Centre for Cyber Security remediation guidance↗CISA KEV record↗CVE authority or vendor reference↗Public exploit reference↗Public exploit reference↗Official CVE record (CNA and ADP data)↗NVD record↗
Technical terms and abbreviations used in this report
CVE
Common Vulnerabilities and Exposures: the public identifier for one disclosed vulnerability.
CVSS
Common Vulnerability Scoring System: a technical severity framework; it is not patching priority by itself.
EPSS
Exploit Prediction Scoring System: FIRST's estimate of the probability that exploitation activity will be observed in the next 30 days; it is a forecast, not confirmation.
CWE
Common Weakness Enumeration: the standard category describing the underlying software or hardware weakness.
CNA
CVE Numbering Authority: an organisation authorised to assign and publish CVE records.
CISA ADP
Cybersecurity and Infrastructure Security Agency Authorized Data Publisher: structured enrichment added to a CVE record.
NVD
National Vulnerability Database: NIST's enrichment service for CVE records.
CERT / CSIRT
A computer security incident response team that publishes warnings or coordinates incident response.
PoC
Proof of concept: public material that demonstrates or helps reproduce exploitation.
CSAF
Common Security Advisory Framework: a machine-readable format for security advisories.
LoTL
Living off the land: abuse of legitimate tools or system functions during an attack.
Free version - for non-commercial use only.CVE-2026-55040 · cve.blacktree.nl