How severe is CVE-2026-21510?

CVE-2026-21510 has a CVSS score of 8.8/10, rated HIGH. Immediate patching is strongly recommended.

Which packages are affected by CVE-2026-21510?

Affected package information for CVE-2026-21510 is not yet fully mapped. Check the official advisory links for details.

How do I fix CVE-2026-21510?

No fixed version has been published for CVE-2026-21510 yet. Monitor the advisory for updates, apply mitigations recommended by the vendor, and use O3 Security to track when a fix becomes available in your stack.

Is CVE-2026-21510 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-21510 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-21510?

CVE-2026-21510 has an EPSS (Exploit Prediction Scoring System) score of 5.2%, placing it in the 90th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

Is CVE-2026-21510 in the CISA Known Exploited Vulnerabilities catalog?

Yes. CVE-2026-21510 (Microsoft Windows Shell Protection Mechanism Failure Vulnerability) was added to CISA's Known Exploited Vulnerabilities (KEV) catalog on 2026-02-10. CISA required all US federal civilian agencies to remediate this vulnerability by 2026-03-03. The required action was: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable. Being listed in the KEV catalog is the strongest possible confirmation of active exploitation — treat this as a critical priority.

What type of vulnerability is CVE-2026-21510?

CVE-2026-21510 is classified as CWE-693 (CWE-693). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

Which products and versions are affected by CVE-2026-21510?

CVE-2026-21510 affects microsoft windows 10 21h2; microsoft windows 10 22h2; microsoft windows 10 1607; microsoft windows 10 1809, and 9 more product(s). Check the affected-products list on this page against your deployed version to confirm exposure.

When was CVE-2026-21510 published, and has it been updated?

CVE-2026-21510 was published on February 10, 2026 and was last updated on February 11, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

CISA KEV·Added 2026-02-10 — agencies required to remediate by 2026-03-03

CVE-2026-21510

HIGH

Protection mechanism failure in Windows Shell allows an unauthorized attacker to bypass a security feature over a network.

Published

Feb 10, 2026

Updated

Feb 11, 2026

Affected

0 pkgs

Patched

None yet

Exploits

None indexed

EPSS Exploitation Probability

via FIRST.org ↗

5.2%probability of exploitation in next 30 days

Lower Risk90th percentile+0.21%

EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.

Description

Protection mechanism failure in Windows Shell allows an unauthorized attacker to bypass a security feature over a network.

Affected Products

13 products · 23 configurations

windows 10 21h2microsoft

< 10.0.19044.6937

range

windows 10 22h2microsoft

< 10.0.19045.6937

range

windows 10 1607microsoft

< 10.0.14393.8868

range

windows 10 1809microsoft

< 10.0.17763.8389

range

windows 11 23h2microsoft

< 10.0.22631.6649

range

windows 11 24h2microsoft

< 10.0.26100.7781

range

Frequently Asked Questions

Protection mechanism failure in Windows Shell allows an unauthorized attacker to bypass a security feature over a network.

O3 Security · Impact-Aware SCA

Is CVE-2026-21510 in your stack?

O3 detects CVE-2026-21510 across dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.

Scan my stack How O3 SCA works