CVE-2026-21509: Microsoft Office Security Feature Bypass Vulnerability.
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.
- CISA KEV-listed (remediation due 2026-02-16)
- EPSS 72.2% (99.4% percentile)
- CVSS 7.8 high
Related briefings
- APT28 Weaponizes CVE-2026-21509 Zero-Day in Operation Neusploit Targeting Eastern Europe 2026-02-02
- CERT-UA Issues Danger Bulletin as APT28 Exploits CVE-2026-21509 Against Ukraine and EU Governments 2026-02-01