CVE-2026-21509
Microsoft Office Security Feature Bypass Vulnerability
KEVHIGH 7.8EPSS 70.8%
Reliance on untrusted inputs in a security decision in Microsoft Office allows an unauthorized attacker to bypass a security feature locally.
- Affected
- Microsoft · Microsoft 365 Apps for Enterprise · Microsoft Office 2016 · Microsoft Office 2019 · Microsoft Office LTSC 2021 · Microsoft Office LTSC 2024
- CVSS v3.1 MICROSOFT
- 7.8 HIGH
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H - EPSS
- 70.80% chance of exploitation in the next 30 days, 99th percentile
- CISA KEV
- added 2026-01-26
- Published
- 2026-01-26
- Updated
- 2026-07-30
Proof-of-concept exploits (7)
- kimstars/Ashwesker-CVE-2026-2150911★ · 2026-01-27
- gavz/CVE-2026-21509-PoC20★ · 2026-01-28
- kaizensecurity/CVE-2026-215090★ · 2026-02-05
- DameDode/CVE-2026-21509-POC0★ · 2026-03-12
- razureink/cve-2026-21509-office_security_bypass_reproduction0★ · 2026-07-23
- IsMyPhonePwned/mimic4★ · 2026-02-05
- SimoesCTT/CTT-NFS-Vortex-RCE3★ · 2026-01-31
Security advisories
- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21509
- https://www.vicarius.io/vsociety/posts/cve-2026-21509-detection-script-microsoft-office-s…
- https://www.vicarius.io/vsociety/posts/cve-2026-21509-mitigation-script-microsoft-office-…