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CVE-2026-21509

Microsoft Office Security Feature Bypass Vulnerability

7.8 HighIn KEVPublic exploit

Reliance on untrusted inputs in a security decision in Microsoft Office allows an unauthorized attacker to bypass a security feature locally.

Attack profile

How easy it is to exploit

Attack vector
Local
Complexity
Low
Privileges needed
None
User interaction
Required

What an attacker can affect

Confidentiality
High
Integrity
High
Availability
High

Exploit likelihood

70.8%Up 57.8 points since Jan 27, 2026
90%50%10%1%

What each source reports

CVE List Score used 7.8

Microsoft Office Security Feature Bypass Vulnerability

Reliance on untrusted inputs in a security decision in Microsoft Office allows an unauthorized attacker to bypass a security feature locally.

Record
CVE-2026-21509
CVSS 3.1
7.8 HighCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C
Weakness
CWE-807
Updated
2026-11-02
EUVDEUVD-2026-4666 7.8

Reliance on untrusted inputs in a security decision in Microsoft Office allows an unauthorized attacker to bypass a security feature locally.

Record
EUVD-2026-4666
CVSS 3.1
7.8 HighCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C
Updated
2026-11-02
GitHub AdvisoriesGHSA-ch84-h92g-mw93 7.8

Reliance on untrusted inputs in a security decision in Microsoft Office allows an unauthorized...

Reliance on untrusted inputs in a security decision in Microsoft Office allows an unauthorized attacker to bypass a security feature locally.

Record
GHSA-ch84-h92g-mw93
CVSS 3.1
7.8 HighCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Weakness
CWE-807
Updated
2026-11-02
CISA KEV No score

Microsoft Office Security Feature Bypass Vulnerability

Microsoft Office contains a security feature bypass vulnerability in which reliance on untrusted inputs in a security decision in Microsoft Office could allow an unauthorized attacker to bypass a security feature locally. Some of the impacted product(s) could be end-of-life (EoL) and/or end-of-service (EoS). Users are advised to discontinue use and/or transition to a supported version.

Record
CVE-2026-21509
Weakness
CWE-807
Updated
2026-11-02
NVD 7.8

Reliance on untrusted inputs in a security decision in Microsoft Office allows an unauthorized attacker to bypass a security feature locally.

Record
CVE-2026-21509
CVSS 3.1
7.8 HighCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Weakness
CWE-807
Updated
2026-11-02

Affected products

Public exploits

Links only. Every CVE stores no exploit code.

Public exploits
SourceLinkDate
PoC in GitHubkimstars/Ashwesker-CVE-2026-215092026-01-27
PoC in GitHubgavz/CVE-2026-21509-PoC2026-01-29
PoC in GitHubksk-itdk/KSK-ITDK-CVE-2026-21509-Mitigation2026-01-29
PoC in GitHubSimoesCTT/CTT-NFS-Vortex-RCE2026-01-31
PoC in GitHubSimoesCTT/SCTT-2026-33-0007-The-OLE-Vortex-Laminar-Bypass-2026-01-31
PoC in GitHubSimoesCTT/CTT-MICROSOFT-OFFICE-OLE-MANIFOLD-BYPASS-CVE-2026-215092026-02-01
PoC in GitHubdecalage2/detect_CVE-2026-215092026-02-04
PoC in GitHubkaizensecurity/CVE-2026-215092026-02-05
PoC in GitHubplanetoid/cve-2026-21509-mitigation2026-02-11
PoC in GitHubsuuhm/CVE-2026-21509-handler2026-03-01
PoC in GitHubDameDode/CVE-2026-21509-POC2026-03-12
PoC in GitHubsentinel-aidefense/CVE-2026-215092026-06-30
PoC in GitHubrazureink/cve-2026-21509-office_security_bypass_reproduction2026-07-23

History

History
RecordedChangedSources
exploitation, exploits
first indexedCVE List, EUVD, GitHub Advisories, CISA KEV, NVD, PoC in GitHub

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2026-21509 is a high vulnerability (CVSS 7.8) in Microsoft Office, published January 26, 2026. CISA lists it as known to be exploited, since January 26, 2026. EUVD reports exploitation since January 26, 2026. Public exploit code exists. EPSS puts the chance of exploitation in the next 30 days at 70.8%, the 99th percentile. No source names a fixed version.

References

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