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Full vulnerability report · 2026
CVE-2026-78504High confidence

Microsoft Office Word Remote Code Execution Vulnerability

Microsoft · Microsoft 365 Apps for Enterprise

8.8HighCVSS 3.1
Recommended action
Within 7 days

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

Patch available
Optional official sources

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

Select the national-authority views to include. The exact source language is shown on each matched advisory. Your choice is remembered on this device and encoded in the shareable URL.

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-2026-73311

No EUVD known-exploited evidence

Stack-based buffer overflow in Microsoft Office Word allows an unauthorized attacker to execute code over a network.

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

Stack-based buffer overflow in Microsoft Office Word allows an unauthorized attacker to execute code over a network.

What

Stack-based buffer overflow in Microsoft Office Word allows an unauthorized attacker to execute code over a network.

Why

A stack-based buffer overflow condition is a condition where the buffer being overwritten is allocated on the stack (i.e., is a local variable or, rarely, a parameter to a function).

How

An attacker operating through a network path may attempt exploitation without authentication after a user interaction. If successful, the issue may execute code or commands in the affected security context.

What

Stack-based buffer overflow in Microsoft Office Word allows an unauthorized attacker to execute code over a network.

Why

A stack-based buffer overflow condition is a condition where the buffer being overwritten is allocated on the stack (i.e., is a local variable or, rarely, a parameter to a function).

How

An attacker operating through a network path may attempt exploitation without authentication after a user interaction. If successful, the issue may execute code or commands in the affected security context.

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 → Stack-based Buffer Overflow → execute code or commands in the affected security context
Attack surface
Network
Privileges required
None: unauthenticated exploitation is possible
User interaction
Required interaction required
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-121 ↗

CWE-121: Stack-based Buffer Overflow. A stack-based buffer overflow condition is a condition where the buffer being overwritten is allocated on the stack (i.e., is a local variable or, rarely, a parameter to a function).

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:R/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.PRNonePrivileges required: The attacker does not need an account or existing privileges.UIRequiredUser interaction: Another user must perform an action for exploitation to succeed.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
After compromise, an attacker may use built-in shells, scripting engines, scheduled tasks and native network utilities for discovery, persistence or movement. This is a plausible LoTL path, not evidence that it has occurred for every attack.
NetworkUnauthenticatedRemote code executionCWE-121
A

Official authority intelligence

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

ENISA EUVD · EUVD-2026-73311Official EUVD mapping

Stack-based buffer overflow in Microsoft Office Word allows an unauthorized attacker to execute code over a network.

Official EUVD record ↗
BSI · German · WID-SEC-2026-3234Microsoft Office Produkte: Mehrere Schwachstellen

Ein Angreifer kann mehrere Schwachstellen in verschiedenen Microsoft Office Produkten, Microsoft Office Online Server, Microsoft 365 Apps, Microsoft SharePoint, Microsoft Teams und Microsoft Skype ausnutzen, um erhöhte Berechtigungen zu erlangen, um Code auszuführen, um Informationen offenzulegen und um den Nutzer zu täuschen.

Official advisory ↗
CERT-FR · French · CERTFR-2026-AVI-1145Multiples vulnérabilités dans Microsoft Office

u 08 septembre 2026 Bulletin de sécurité Microsoft Office CVE-2026-72976 du 08 septembre 2026 Bulletin de sécurité Microsoft Office CVE-2026-72977 du 08 septembre 2026 Bulletin de sécurité Microsoft Office CVE-2026-77898 du 08 septembre 2026 Bulletin de sécurité Microsoft Office CVE-2026-77901 du 08 septembre 2026 Bulletin de sécurité Microsoft Office CVE-2026-77911 du 08 septembre 2026 Bulletin de sécurité Microsoft Office CVE-2026-78439 du 08 septembre 2026 Bulletin de sécurité Microsoft Office CVE-2026-78502 du 08 septembre 2026 Bulletin de sécurité Microsoft Office CVE-2026-78503 du 08 septembre 2026 Bulletin de sécurité Microsoft Office CVE-2026-78504 du 08 septembre 2026 Bulletin de sécurité Microsoft Office CVE-2026-78505 du 08 septembre 2026 Bulletin de sécurité Microsoft Office CVE-2026-78506 du 08 septembre 2026 Bulletin de sécurité Microsoft Office CVE-2026-78507 du 08 septembre 2026 Bulletin de sécurité Microsoft Office CVE-2026-78509 du 08 septembre 2026 Bulletin de sécurité Microsoft Office CVE-2026-78510 du 08 septembre 2026 Bulletin de sécurité Microsoft Office CVE-2026-78511 du 08 septembre 2026 Bulletin de sécurité Microsoft Office CVE-2026-78512 du 08 septembre 2026 Bulletin de sécurité Microsoft Office CVE-2026-78513 du 08 septembre 2026 Bulletin de sécurité Microsoft Offic

Official advisory ↗
CSIRT Italia · Italian · aggiornamenti-mensili-microsoft-24Aggiornamenti Mensili Microsoft

nuova finestra - - CVE-2026-78452 : apre una nuova finestra - - CVE-2026-78453 : apre una nuova finestra - - CVE-2026-78454 : apre una nuova finestra - - CVE-2026-78455 : apre una nuova finestra - - CVE-2026-78456 : apre una nuova finestra - - CVE-2026-78457 : apre una nuova finestra - - CVE-2026-80093 : apre una nuova finestra - - CVE-2026-80091 : apre una nuova finestra - - CVE-2026-80097 : apre una nuova finestra - - CVE-2026-80098 : apre una nuova finestra - - CVE-2026-78461 : apre una nuova finestra - - CVE-2026-78462 : apre una nuova finestra - - CVE-2026-80096 : apre una nuova finestra - - CVE-2026-81349 : apre una nuova finestra - - CVE-2026-78504 : apre una nuova finestra - - CVE-2026-83939 : apre una nuova finestra - - CVE-2026-78505 : apre una nuova finestra - - CVE-2026-78506 : apre una nuova finestra - - CVE-2026-78507 : apre una nuova finestra - - CVE-2026-78508 : apre una nuova finestra - - CVE-2026-78509 : apre una nuova finestra - - CVE-2026-78463 : apre una nuova finestra - - CVE-2026-78464 : apre una nuova finestra - - CVE-2026-78502 : apre una nuova finestra - - CVE-2026-78503 : apre una nuova finestra - - CVE-2026-81352 : apre una nuova finestra - - CVE-2026-81356 : apre una nuova finestra - - CVE-2026-81355 : apre una nuova finestra - - CVE-2026-81354 : apre una nuova fi

Official advisory ↗
NCSC-NL · Dutch · NCSC-2026-0352Kwetsbaarheden verholpen in Microsoft Office

Een kwaadwillende kan de kwetsbaarheden misbruiken om aanvallen uit te voeren die kunnen leiden tot de categorieën schade, zoals genoemd in onderstaande tabel. Voor succesvol misbruik moet de kwaadwillende het slachtoffer misleiden een malafide bestand te openen of link te volgen. Microsoft heeft voor Office 114 kwetsbaarheden verholpen. De 4 ernstigste kwetsbaarheden bevinden zich in meerdere Office componenten en hebben een CVSS score van 9.8 toegewezen gekregen. Kwaadwillenden met toegang tot deze componenten kunnen zonder voorafgaande authenticatie mogelijk code uitvoeren of zich toegang verschaffen tot het kwetsbare systeem. Deze kwetsbaarheden zijn in onderstaande tabel weergegeven. De overige 110 kwetsbaarheden variëren in ernst van middelmatig tot hoog en kritiek. Raapleeg het MSRC-portaal voor aanvullende informatie. ``` |----------------|------|---------------------------|-------------------------------------| | CVE-ID | CVSS | Component | Impact | |----------------|------|---------------------------|-------------------------------------| | CVE-2026-78505 | 9,80 | Office | Uitvoeren van willekeurige code | |----------------|------|---------------------------|-------------------------------------| | CVE-2026-78509 | 9,80 | Outlook | Uitvoeren van willekeurige code | |----------------|------|---------------------------|-------------------------------------| | CVE-2026-78510 | 9,80 | Outlook | Uitvoeren van willekeurige code | |----------------|------|---------------------------|-------------------------------------| | CVE-2026-66302 | 9,80 | SKYPE | Uitvoeren van willekeurige code | |----------------|------|---------------------------|-------------------------------------| ```

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
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.
Action
Review the linked authoritative reference and apply the recorded fixed release appropriate to the affected product branch.
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 8 Sept 2026 · Last source change 11 Sept 2026, 16:40 UTC · CWE-121 · Stack-based Buffer Overflow

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 2026-09-09
European sourceENISA EUVD · EUVD-2026-73311
Product sourceCNA
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. ENISA EUVD mappingEUVD-2026-73311 was added to the official ENISA EUVD mapping for this CVE.
    Before
    not recorded
    After
    {"euvdId":"EUVD-2026-73311"}
    ENISA EUVD ↗
  2. Vendor guidanceAuthoritative vendor guidance changed from no authoritative guidance recorded to authoritative remediation link · patch.
    Before
    no authoritative guidance recorded
    After
    authoritative remediation link · patch
    secure@microsoft.com ↗
  3. Affected versionsThe structured affected or fixed version information changed.
    Before
    16.0.1 < 16.0.20326.20138; 19.0.0 < 16.0.10417.20207; -; 16.0.1 < 16.0.14334.20906; 16.0.0 < 16.0.17932.20976; 16.0.1 < 16.0.5569.1000 · Fixed: No fixed version is explicitly recorded in the structured CVE data.
    After
    16.0.1 < 16.0.20326.20138; 19.0.0 < 16.0.10417.20207; -; 16.0.1 < 16.0.14334.20906; 16.0.0 < 16.0.17932.20976; 16.0.1 < 16.0.5569.1000 · 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 ↗
  4. Remediation statusRemediation status changed from Awaiting fix to Patch available.
    Before
    Awaiting fix
    After
    Patch available
    secure@microsoft.com ↗
  5. Catalogue recordCVE added to the BlackTree catalogue.
    CNA ↗
Material fields only · duplicate refreshes suppressed · history retained for the configured operational retention period
CVE published
Fixed release or patch reference recorded
ENISA EUVD · EUVD-2026-73311↗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-2026-78504 · cve.blacktree.nl