- High 7.8
- Known exploited (CISA KEV)
CVE-2026-21509
Reliance on untrusted inputs in a security decision in Microsoft Office allows an unauthorized attacker to bypass a security feature locally.
Scores
The facts
- Published
- 26 January 2026
- Last changed
- 25 June 2026
- NVD status
- Analyzed
- Severity
- High, CVSS 7.8 out of 10 (version 3.1)
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H - Weakness
- Affects
- microsoft 365 apps
- microsoft office
- microsoft office long term servicing channel
- Known exploited
- Yes. CISA added it to the Known Exploited Vulnerabilities catalogue on 26 January 2026.
- EPSS
- 70.8% chance of exploitation activity in the next 30 days (percentile 99).
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