CVE-2026-21510

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 Windows Shell allows an unauthorized attacker to bypass a security feature over a network.

References

msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21510 · Vendor Advisory
www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-21510 · US Government Resource