Microsoft Office Security Feature Bypass Vulnerability (CVE-2026-21509)
Severity: high · Patch status: unknown · Since 2026-01-26 · CVE-2026-21509
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. CISA added CVE-2026-21509 to its Known Exploited Vulnerabilities catalog on Jan 26, 2026, which means attackers are exploiting it in the wild.
What to do
- Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
- US federal agencies must remediate by Feb 16, 2026 (BOD 22-01); treat that as the outer limit.
Sources
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