CVE-2026-21509
Microsoft Office Security Feature Bypass Vulnerability
In short
Microsoft Office accepts untrusted data when making security decisions, allowing someone on your computer to bypass built-in security protections. This could let malicious content run when it should be blocked.
Technical detail
CWE-807 vulnerability in Microsoft Office's security decision logic trusts user-controllable input to determine security policy enforcement. Local attacker can manipulate inputs to circumvent access controls or content restrictions; requires local access but bypasses intended security boundaries.
Summary generated and translated by AI from the official description.
Reliance on untrusted inputs in a security decision in Microsoft Office allows an unauthorized attacker to bypass a security feature locally.
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C
Affected products
Microsoft · Microsoft 365 Apps for EnterpriseMicrosoft · Microsoft Office 2016Microsoft · Microsoft Office 2019Microsoft · Microsoft Office LTSC 2021Microsoft · Microsoft Office LTSC 2024Want to know if your infrastructure is exposed to this?
Talk to TrueHacking →References
https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21509https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-21509https://www.vicarius.io/vsociety/posts/cve-2026-21509-detection-script-microsoft-office-security-feature-bypass-vulnerabilityhttps://www.vicarius.io/vsociety/posts/cve-2026-21509-mitigation-script-microsoft-office-security-feature-bypass-vulnerability