CVSS 7.8ACTIVELY EXPLOITED4 sources verified·1 min read
By Lyrie Threat Intelligence·6/25/2026
HIGH: CVE-2026-21509 actively exploited — microsoft 365 apps
CVE: CVE-2026-21509
CVSS: 7.8 (3.1) — CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
Severity: HIGH
Status: ✅ Confirmed exploited in the wild (CISA KEV)
Affected
- microsoft 365 apps
- microsoft office
- microsoft office long term servicing channel
Summary
Reliance on untrusted inputs in a security decision in Microsoft Office allows an unauthorized attacker to bypass a security feature locally.
Verified Sources
References
- https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21509
- https://www.vicarius.io/vsociety/posts/cve-2026-21509-detection-script-microsoft-office-security-feature-bypass-vulnerability
- https://www.vicarius.io/vsociety/posts/cve-2026-21509-mitigation-script-microsoft-office-security-feature-bypass-vulnerability
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-21509
_Validated by the Lyrie Threat Intelligence Pipeline — 3 independent sources confirmed before publication. No speculation._
Lyrie Verdict
Lyrie's autonomous detection layer catches active exploitation primitives at machine speed — closing the gap between disclosure and weaponization that traditional defense simply can't cover.
Validated sources
- [1]NVD
- [2]GitHub Advisory
- [3]MITRE
- [4]CISA KEV
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