Exploited vulnerability

CVE-2026-21509

TLP:CLEAR

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.

Facts

Vendor: Microsoft
Product: Office
CVSS: 7.8
EPSS (probability of exploitation within 30 days): 70.8 %
On CISA's Known Exploited Vulnerabilities list since: 26 January 2026
First known exploitation: 26 January 2026
CISA's deadline for US federal agencies: 16 February 2026
Weakness: CWE-807
First seen by Risk Letters: 26 January 2026

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Data: NVD (public domain), CISA KEV, FIRST EPSS, MITRE ATT&CK, AlienVault OTX. NVD