CVE-2026-21509
Act now ● On CISA KEV — actively exploited
Actively exploited — on the CISA KEV list.
CVSS base
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EPSS — probability of exploitation (30 days)
72.6%
99.4th percentile
CISA KEV
Listed
Added 2026-01-26 · patch by 2026-02-16
Weakness / dates
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Published — · modified —
Timeline
- 2026-01-26 — Added to CISA KEV (actively exploited)
- 2026-02-16 — CISA patch-by deadline
Description
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.