How severe is CVE-2025-21418?

CVE-2025-21418 has a CVSS score of 7.8/10, rated HIGH. Immediate patching is strongly recommended.

Which packages are affected by CVE-2025-21418?

Affected package information for CVE-2025-21418 is not yet fully mapped. Check the official advisory links for details.

How do I fix CVE-2025-21418?

No fixed version has been published for CVE-2025-21418 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-2025-21418 actively exploited in the wild?

No public exploit code has been indexed for CVE-2025-21418 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-2025-21418?

CVE-2025-21418 has an EPSS (Exploit Prediction Scoring System) score of 10.3%, placing it in the 93th 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 warrants monitoring and prompt remediation.

Is CVE-2025-21418 in the CISA Known Exploited Vulnerabilities catalog?

Yes. CVE-2025-21418 (Microsoft Windows Ancillary Function Driver for WinSock Heap-Based Buffer Overflow Vulnerability) was added to CISA's Known Exploited Vulnerabilities (KEV) catalog on 2025-02-11. CISA required all US federal civilian agencies to remediate this vulnerability by 2025-03-04. The required action was: Apply mitigations per vendor instructions 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-2025-21418?

CVE-2025-21418 is classified as CWE-122 (CWE-122). 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-2025-21418?

CVE-2025-21418 affects microsoft windows 10 21h2; microsoft windows 10 22h2; microsoft windows 10 1607; microsoft windows 10 1809, and 10 more product(s). Check the affected-products list on this page against your deployed version to confirm exposure.

When was CVE-2025-21418 published, and has it been updated?

CVE-2025-21418 was published on February 11, 2025 and was last updated on October 27, 2025. 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 2025-02-11 — agencies required to remediate by 2025-03-04

CVE-2025-21418

HIGH

Windows Ancillary Function Driver for WinSock Elevation of Privilege Vulnerability

Published

Feb 11, 2025

Updated

Oct 27, 2025

Affected

0 pkgs

Patched

None yet

Exploits

None indexed

EPSS Exploitation Probability

via FIRST.org ↗

10.3%probability of exploitation in next 30 days

Moderate Risk93th percentile-2.98%

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

Windows Ancillary Function Driver for WinSock Elevation of Privilege Vulnerability

Affected Products

14 products · 18 configurations

windows 10 21h2microsoft

< 10.0.19044.5487

range

windows 10 22h2microsoft

< 10.0.19045.5487

range

windows 10 1607microsoft

< 10.0.10240.20915

range

windows 10 1809microsoft

< 10.0.17763.6893

range

windows 11 22h2microsoft

< 10.0.22621.4890

range

windows 11 23h2microsoft

< 10.0.22631.4890

range

Frequently Asked Questions

Windows Ancillary Function Driver for WinSock Elevation of Privilege Vulnerability

O3 Security · Impact-Aware SCA

Is CVE-2025-21418 in your stack?

O3 detects CVE-2025-21418 across dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.

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