BlackTreeCVE Intelligence
← Back to the CVE catalogue
Full vulnerability report · 2026
CVE-2026-96940High confidence

Microsoft Exchange Server Elevation of Privilege Vulnerability

Microsoft · Microsoft Exchange Server 2016 Cumulative Update 23

8.8HighCVSS 3.1
Recommended action
Within 7 days

High technical severity; prioritise exposed affected systems while verifying vendor guidance.

Patch available
R
Operational reassessment

Published severity in operational context

Open reassessment dashboard →
Published severityHighOperational priority:High, unchanged from published severity.unchanged

Evidence used

  • No CISA KEV confirmation is currently recorded.
  • EPSS is 0.50% 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.
  • Monitor vendor guidance and exploitation sources for a material change.

Verification

  1. Confirm that the asset runs Microsoft Microsoft Exchange Server 2016 Cumulative Update 23 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 30 daysRemediation target: Within 180 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.

Direct vendor intelligence

Authoritative vendor CSAF and VEX advisories

Structured product status and remediation from the issuing vendor. Product-state explanations are always visible; large lists can be searched or downloaded.

1 current
msrc_CVE-2026-96940 · CSAF 2.0 · revision 1 · finalMicrosoft Security Response CenterMicrosoft Exchange Server Elevation of Privilege Vulnerability
4 known affected

The vendor explicitly identifies these products as affected by this CVE.

  • Microsoft Exchange Server Subscription Edition RTM <15.02.2562.053
  • Microsoft Exchange Server 2019 Cumulative Update 15 <15.02.1748.053
  • Microsoft Exchange Server 2019 Cumulative Update 14 <15.02.1544.048
  • Microsoft Exchange Server 2016 Cumulative Update 23 <15.01.2507.075
Summary
Microsoft
Remediation
15.02.1544.048:Security Update:https://support.microsoft.com/help/5129957
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-2026-91771

No EUVD known-exploited evidence

An elevation of privilege vulnerability exists when Microsoft Exchange Outlook Web Access (OWA) fails to properly handle web requests. An attacker who successfully exploited this vulnerability could perform script/content injection attacks and attempt to trick the user into disclosing sensitive information. To exploit the vulnerability, an attacker could send a specially crafted email message containing a malicious link to a user. Alternatively, an attacker could use a chat client to social engineer a user into clicking the malicious link. The security update addresses the vulnerability by correcting how Microsoft Exchange validates web requests. Note: In order to exploit this vulnerability, a user must click a maliciously crafted link from an attacker.

EUVD state
Present in the current official mapping
Known exploitation
Not present in the current ENISA EUVD known-exploited dataset. This is not proof of no exploitation.
ENISA score
8.8 · CVSS 3.1
Advisory evidence
No linked advisory details stored yet
Recommended actionWithin 7 days

High technical severity; prioritise exposed affected systems while verifying vendor guidance.

Patch available
01

What, why and how

An elevation of privilege vulnerability exists when Microsoft Exchange Outlook Web Access (OWA) fails to properly handle web requests. An attacker who successfully exploited this vulnerability could perform script/content injection attacks and attempt to trick the user into disclosing sensitive information. To exploit the vulnerability, an attacker could send a specially crafted email message containing a malicious link to a user. Alternatively, an attacker could use a chat client to social engineer a user into clicking the malicious link. The security update addresses the vulnerability by correcting how Microsoft Exchange validates web requests. Note: In order to exploit this vulnerability, a user must click a maliciously crafted link from an attacker.

What

An elevation of privilege vulnerability exists when Microsoft Exchange Outlook Web Access (OWA) fails to properly handle web requests. An attacker who successfully exploited this vulnerability could perform script/content injection attacks and attempt to trick the user into disclosing sensitive information. To exploit the vulnerability, an attacker could send a specially crafted email message containing a malicious link to a user. Alternatively, an attacker could use a chat client to social engineer a user into clicking the malicious link. The security update addresses the vulnerability by correcting how Microsoft Exchange validates web requests. Note: In order to exploit this vulnerability, a user must click a maliciously crafted link from an attacker.

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 with low privileges. If successful, the issue may gain additional privileges.

What

An elevation of privilege vulnerability exists when Microsoft Exchange Outlook Web Access (OWA) fails to properly handle web requests. An attacker who successfully exploited this vulnerability could perform script/content injection attacks and attempt to trick the user into disclosing sensitive information. To exploit the vulnerability, an attacker could send a specially crafted email message containing a malicious link to a user. Alternatively, an attacker could use a chat client to social engineer a user into clicking the malicious link. The security update addresses the vulnerability by correcting how Microsoft Exchange validates web requests. Note: In order to exploit this vulnerability, a user must click a maliciously crafted link from an attacker.

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 with low privileges. If successful, the issue may gain additional privileges.

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.
No confirmed evidence

No CISA KEV match was present at the last successful refresh. This means no confirmation from that source, not proof of no exploitation.

Public PoC / exploit material
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
None recorded

No exploit-tagged reference or CISA SSVC proof-of-concept state is currently recorded. Research may still exist outside the structured feeds.

Likely attack path
a network path → Weak Authentication → gain additional privileges
Attack surface
Network
Privileges required
Low: a basic authenticated account is required
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:L/UI:N/S:U/C:H/I:H/A:H/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.PRLowPrivileges required: The attacker needs basic user-level 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.AHighAvailability impact: A successful attack can cause a major loss.
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.
NetworkPrivilege escalationCWE-1390
A

Official authority intelligence

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

ENISA EUVD · EUVD-2026-91771Official EUVD mapping

An elevation of privilege vulnerability exists when Microsoft Exchange Outlook Web Access (OWA) fails to properly handle web requests. An attacker who successfully exploited this vulnerability could perform script/content injection attacks and attempt to trick the user into disclosing sensitive information. To exploit the vulnerability, an attacker could send a specially crafted email message containing a malicious link to a user. Alternatively, an attacker could use a chat client to social engineer a user into clicking the malicious link. The security update addresses the vulnerability by correcting how Microsoft Exchange validates web requests. Note: In order to exploit this vulnerability, a user must click a maliciously crafted link from an attacker.

Official EUVD record ↗
BSI · German · WID-SEC-2026-3718Microsoft Exchange Server: Schwachstelle ermöglicht Privilegieneskalation

Ein entfernter, authentisierter Angreifer kann eine Schwachstelle in Microsoft Exchange Server ausnutzen, um seine Privilegien zu erhöhen, wodurch er Zugriff auf die Postfächer anderer Benutzer innerhalb derselben Organisation erhält und E-Mail-Nachrichten sowie Anhänge lesen kann.

Official advisory ↗
Canadian Centre for Cyber Security · English · AV26-1001Microsoft security advisory (AV26-1001)

As of October 2, 2026, Microsoft is affected by a vulnerability in the following products:

Official advisory ↗
Cyber Security Agency of Singapore · English · CSA-SB-20261007Security Bulletin 7 Oct 2026

The Cyber Security Agency of Singapore included this CVE in its official Security Bulletin 7 Oct 2026, published on 7 October 2026. Open the linked bulletin for the product, severity and reference information published in that issue.

Official advisory ↗
CERT-FR · French · CERTFR-2026-AVI-1258Vulnérabilité dans Microsoft Exchange Server

Une vulnérabilité a été découverte dans Microsoft Exchange Server. Elle permet à un attaquant de provoquer une élévation de privilèges.

Official advisory ↗
NCSC-NL · Dutch · NCSC-2026-0401Kwetsbaarheid verholpen in Microsoft Exchange Server

A weakness in authorization within Microsoft Exchange Server enables an authenticated attacker to escalate privileges remotely over a network.

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
Action
15.02.1544.048:Security Update:https://support.microsoft.com/help/5129957
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 2 Oct 2026 · Last source change 8 Oct 2026, 22:15 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 2026-10-03
European sourceENISA EUVD · EUVD-2026-91771
Product sourceVendor CSAF · Microsoft Security Response Center
Remediation sourceVendor CSAF · Microsoft Security Response Center
CWE sourceOther authority
NVD statusNVD enrichment underway

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: removed patch: msrc.microsoft.com/CVE-2026-96940; removed remediation: msrc.microsoft.com/CVE-2026-96940.
    Before
    patch: msrc.microsoft.com/CVE-2026-96940 · remediation: msrc.microsoft.com/CVE-2026-96940
    After
    no authoritative guidance recorded
    CNA ↗
  2. Affected versionsThe structured affected or fixed version information changed.
    Before
    Microsoft Exchange Server 2016 Cumulative Update 23: 15.01.0.0 < 15.01.2507.075; Microsoft Exchange Server 2019 Cumulative Update 14: 15.02.0.0 < 15.02.1544.048; Microsoft Exchange Server 2019 Cumulative Update 15: 15.02.0.0 < 15.02.1748.053; Microsoft Exchange Server Subscription Edition RTM: 15.02.0.0 < 15.02.2562.053 · Fixed: 15.02.1544.048:Security Update:https://support.microsoft.com/help/5129957
    After
    Microsoft Exchange Server 2016 Cumulative Update 23: 15.01.0.0 < 15.01.2507.075; Microsoft Exchange Server 2019 Cumulative Update 14: 15.02.0.0 < 15.02.1544.048; Microsoft Exchange Server 2019 Cumulative Update 15: 15.02.0.0 < 15.02.1748.053; Microsoft Exchange Server Subscription Edition RTM: 15.02.0.0 < 15.02.2562.053 · Fixed: No fixed version is explicitly recorded in the structured CVE data.
    CNA ↗
  3. Remediation statusRemediation status changed from Patch available to Awaiting fix.
    Before
    Patch available
    After
    Awaiting fix
    CNA ↗
  4. Vendor guidanceAuthoritative vendor guidance changed: removed patch: msrc.microsoft.com/CVE-2026-96940; removed remediation: msrc.microsoft.com/CVE-2026-96940.
    Before
    patch: msrc.microsoft.com/CVE-2026-96940 · remediation: msrc.microsoft.com/CVE-2026-96940
    After
    no authoritative guidance recorded
    CNA ↗
  5. Affected versionsThe structured affected or fixed version information changed.
    Before
    Microsoft Exchange Server 2016 Cumulative Update 23: 15.01.0.0 < 15.01.2507.075; Microsoft Exchange Server 2019 Cumulative Update 14: 15.02.0.0 < 15.02.1544.048; Microsoft Exchange Server 2019 Cumulative Update 15: 15.02.0.0 < 15.02.1748.053; Microsoft Exchange Server Subscription Edition RTM: 15.02.0.0 < 15.02.2562.053 · Fixed: 15.02.1544.048:Security Update:https://support.microsoft.com/help/5129957
    After
    Microsoft Exchange Server 2016 Cumulative Update 23: 15.01.0.0 < 15.01.2507.075; Microsoft Exchange Server 2019 Cumulative Update 14: 15.02.0.0 < 15.02.1544.048; Microsoft Exchange Server 2019 Cumulative Update 15: 15.02.0.0 < 15.02.1748.053; Microsoft Exchange Server Subscription Edition RTM: 15.02.0.0 < 15.02.2562.053 · Fixed: No fixed version is explicitly recorded in the structured CVE data.
    CNA ↗
  6. Remediation statusRemediation status changed from Patch available to Awaiting fix.
    Before
    Patch available
    After
    Awaiting fix
    CNA ↗
  7. Vendor guidanceAuthoritative vendor guidance changed: removed patch: msrc.microsoft.com/CVE-2026-96940; removed remediation: msrc.microsoft.com/CVE-2026-96940.
    Before
    patch: msrc.microsoft.com/CVE-2026-96940 · remediation: msrc.microsoft.com/CVE-2026-96940
    After
    no authoritative guidance recorded
    CNA ↗
  8. Affected versionsThe structured affected or fixed version information changed.
    Before
    Microsoft Exchange Server 2016 Cumulative Update 23: 15.01.0.0 < 15.01.2507.075; Microsoft Exchange Server 2019 Cumulative Update 14: 15.02.0.0 < 15.02.1544.048; Microsoft Exchange Server 2019 Cumulative Update 15: 15.02.0.0 < 15.02.1748.053; Microsoft Exchange Server Subscription Edition RTM: 15.02.0.0 < 15.02.2562.053 · Fixed: 15.02.1544.048:Security Update:https://support.microsoft.com/help/5129957
    After
    Microsoft Exchange Server 2016 Cumulative Update 23: 15.01.0.0 < 15.01.2507.075; Microsoft Exchange Server 2019 Cumulative Update 14: 15.02.0.0 < 15.02.1544.048; Microsoft Exchange Server 2019 Cumulative Update 15: 15.02.0.0 < 15.02.1748.053; Microsoft Exchange Server Subscription Edition RTM: 15.02.0.0 < 15.02.2562.053 · Fixed: No fixed version is explicitly recorded in the structured CVE data.
    CNA ↗
  9. Remediation statusRemediation status changed from Patch available to Awaiting fix.
    Before
    Patch available
    After
    Awaiting fix
    CNA ↗
  10. ENISA EUVD mappingEUVD-2026-91771 was added to the official ENISA EUVD mapping for this CVE.
    Before
    not recorded
    After
    {"euvdId":"EUVD-2026-91771"}
    ENISA EUVD ↗
  11. Vendor guidanceAuthoritative vendor guidance changed: removed patch: msrc.microsoft.com/CVE-2026-96940; removed remediation: msrc.microsoft.com/CVE-2026-96940.
    Before
    patch: msrc.microsoft.com/CVE-2026-96940 · remediation: msrc.microsoft.com/CVE-2026-96940
    After
    no authoritative guidance recorded
    CNA ↗
  12. Affected versionsThe structured affected or fixed version information changed.
    Before
    Microsoft Exchange Server 2016 Cumulative Update 23: 15.01.0.0 < 15.01.2507.075; Microsoft Exchange Server 2019 Cumulative Update 14: 15.02.0.0 < 15.02.1544.048; Microsoft Exchange Server 2019 Cumulative Update 15: 15.02.0.0 < 15.02.1748.053; Microsoft Exchange Server Subscription Edition RTM: 15.02.0.0 < 15.02.2562.053 · Fixed: 15.02.1544.048:Security Update:https://support.microsoft.com/help/5129957
    After
    Microsoft Exchange Server 2016 Cumulative Update 23: 15.01.0.0 < 15.01.2507.075; Microsoft Exchange Server 2019 Cumulative Update 14: 15.02.0.0 < 15.02.1544.048; Microsoft Exchange Server 2019 Cumulative Update 15: 15.02.0.0 < 15.02.1748.053; Microsoft Exchange Server Subscription Edition RTM: 15.02.0.0 < 15.02.2562.053 · Fixed: No fixed version is explicitly recorded in the structured CVE data.
    CNA ↗
  13. Remediation statusRemediation status changed from Patch available to Awaiting fix.
    Before
    Patch available
    After
    Awaiting fix
    CNA ↗
  14. Catalogue recordCVE added to the BlackTree catalogue.
    CNA ↗
  15. CVSS scoreCVSS vector changed while the displayed base score remained 8.8.
    Before
    8.8 (CVSS 3.1 · CNA · CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H)
    After
    8.8 (CVSS 3.1 · CNA · CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C)
    CNA ↗
  16. Affected versionsThe structured affected or fixed version information changed.
    Before
    Microsoft Exchange Server 2016 Cumulative Update 23: 15.01.0.0 < 15.01.2507.075; Microsoft Exchange Server 2019 Cumulative Update 14: 15.02.0.0 < 15.02.1544.048; Microsoft Exchange Server 2019 Cumulative Update 15: 15.02.0.0 < 15.02.1748.053; Microsoft Exchange Server Subscription Edition RTM: 15.02.0.0 < 15.02.2562.053 · Fixed: No fixed version is explicitly recorded in the structured CVE data.
    After
    Microsoft Exchange Server 2016 Cumulative Update 23: 15.01.0.0 < 15.01.2507.075; Microsoft Exchange Server 2019 Cumulative Update 14: 15.02.0.0 < 15.02.1544.048; Microsoft Exchange Server 2019 Cumulative Update 15: 15.02.0.0 < 15.02.1748.053; Microsoft Exchange Server Subscription Edition RTM: 15.02.0.0 < 15.02.2562.053 · Fixed: 15.02.1544.048:Security Update:https://support.microsoft.com/help/5129957
    Microsoft Security Response Center ↗
  17. Remediation statusRemediation status changed from Awaiting fix to Patch available.
    Before
    Awaiting fix
    After
    Patch available
    Microsoft Security Response Center ↗
Material fields only · duplicate refreshes suppressed · history retained for the configured operational retention period
CVE published
Fixed release recorded from official guidance
ENISA EUVD · EUVD-2026-91771↗CVE authority or vendor 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-2026-96940 · cve.blacktree.nl