CVE-2026-21513
Microsoft Windows 10 Version 1607, Microsoft Windows 10 Version 1809, Microsoft Windows 10 Version 21H2
Published 10 Feb 2026 · updated 17 Jun 2026 · Analyzed
8.8 High · CVSS 3.1, microsoft.com
Exploited in the wild
CISA added this to its Known Exploited Vulnerabilities catalog on 10 Feb 2026, with a remediation deadline of 3 Mar 2026 for US federal agencies.
Required action: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
Description
Protection mechanism failure in MSHTML Framework allows an unauthorized attacker to bypass a security feature over a network.
References
- msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21513 · Vendor Advisory
- www.vicarius.io/vsociety/posts/cve-2026-21513-detection-script-security-feature-bypass-vulnerability-in-mshtml-framework · Third Party Advisory
- www.vicarius.io/vsociety/posts/cve-2026-21513-mitigation-script-security-feature-bypass-vulnerability-in-mshtml-framework · Mitigation, Third Party Advisory
- www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-21513 · US Government Resource