Microsoft Windows Shell Protection Mechanism Failure Vulnerability

HIGH 8.8EXPLOITED (CISA KEV)CVE-2026-21510 · Published 10/02/2026 · updated 17/06/2026

Microsoft Windows Shell Protection Mechanism Failure Vulnerability. Actively exploited: CISA added this vulnerability to its Known Exploited Vulnerabilities catalog on 10/02/2026. Patch affected systems as an emergency.

In short

CVE-2026-21510 is a HIGH (CVSS 8.8) vulnerability.
Exploited in the wild: CISA added it to the KEV catalog on 10/02/2026.
Chance of exploitation in the next 30 days (EPSS): 61.2%, higher than 99.2% of all vulnerabilities.
No patched version is listed yet: follow the vendor's advisory in References.

Package	Affected versions	Patched versions
Windows Microsoft	Versions not published yet (product named by CISA KEV)

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
cisa.gov/known-exploited-vulnerabilities-catalog · US Government Resource
CISA KEV · CVE-2026-21510

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