CVE-2025-21418: Windows Ancillary Function Driver for WinSock Elevation of Privilege Vulnerability

Severity: high (CVSS 7.8 v3.1)
Exploited in the wild: yes — in CISA KEV since 2025-02-11
EPSS: 2.1% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2025-02-11 · updated 2026-06-17
Weakness: CWE-122

Description

Windows Ancillary Function Driver for WinSock Elevation of Privilege Vulnerability

Affected products

Microsoft Windows 10 1607: before 10.0.10240.20915 — fixed in 10.0.10240.20915
Microsoft Windows 10: before 10.0.17763.6893 — fixed in 10.0.17763.6893
Microsoft Windows 10: before 10.0.19044.5487 — fixed in 10.0.19044.5487
Microsoft Windows 10: before 10.0.19045.5487 — fixed in 10.0.19045.5487
Microsoft Windows 11: before 10.0.22621.4890 — fixed in 10.0.22621.4890
Microsoft Windows 11: before 10.0.22631.4890 — fixed in 10.0.22631.4890
Microsoft Windows 11: before 10.0.26100.3107 — fixed in 10.0.26100.3107
Microsoft Windows Server 2008: r2-sp1
Microsoft Windows Server 2012: r2
Microsoft Windows Server 2016: before 10.0.14393.7785 — fixed in 10.0.14393.7785
Microsoft Windows Server 2019: before 10.0.17763.6893 — fixed in 10.0.17763.6893
Microsoft Windows Server 2022: before 10.0.20348.3148 — fixed in 10.0.20348.3148
Microsoft Windows Server 2022, 23H2 Edition (Server Core installation): before 10.0.25398.1425 — fixed in 10.0.25398.1425
Microsoft Windows Server 2025: before 10.0.26100.3107 — fixed in 10.0.26100.3107
Microsoft Windows 10 Version 1507: from 10.0.10240.0 before 10.0.10240.20915 — fixed in 10.0.10240.20915
Microsoft Windows 10 1607: from 10.0.14393.0 before 10.0.14393.7785 — fixed in 10.0.14393.7785
Microsoft Windows 10: from 10.0.17763.0 before 10.0.17763.6893 — fixed in 10.0.17763.6893
Microsoft Windows 10: from 10.0.19044.0 before 10.0.19044.5487 — fixed in 10.0.19044.5487
Microsoft Windows 10: from 10.0.19045.0 before 10.0.19045.5487 — fixed in 10.0.19045.5487
Microsoft Windows 11: from 10.0.22621.0 before 10.0.22621.4890 — fixed in 10.0.22621.4890
Microsoft Windows 11 version 22H3: from 10.0.22631.0 before 10.0.22631.4890 — fixed in 10.0.22631.4890
Microsoft Windows 11: from 10.0.22631.0 before 10.0.22631.4890 — fixed in 10.0.22631.4890
Microsoft Windows 11: from 10.0.26100.0 before 10.0.26100.3194 — fixed in 10.0.26100.3194
Microsoft Windows Server 2008 R2 Service Pack 1: from 6.1.7601.0 before 6.1.7601.27566 — fixed in 6.1.7601.27566
Microsoft Windows Server 2008 Service Pack 2: from 6.0.6003.0 before 6.0.6003.23117 — fixed in 6.0.6003.23117
Microsoft Windows Server 2012: from 6.2.9200.0 before 6.2.9200.25317 — fixed in 6.2.9200.25317
Microsoft Windows Server 2012 R2: from 6.3.9600.0 before 6.3.9600.22417 — fixed in 6.3.9600.22417
Microsoft Windows Server 2016: from 10.0.14393.0 before 10.0.14393.7785 — fixed in 10.0.14393.7785
Microsoft Windows Server 2019: from 10.0.17763.0 before 10.0.17763.6893 — fixed in 10.0.17763.6893
Microsoft Windows Server 2022: from 10.0.20348.0 before 10.0.20348.3207 — fixed in 10.0.20348.3207

How to fix

Upgrade to a fixed version: Microsoft Windows 10 1607 10.0.10240.20915; Microsoft Windows 10 10.0.17763.6893; Microsoft Windows 10 10.0.19044.5487; Microsoft Windows 10 10.0.19045.5487; Microsoft Windows 11 10.0.22621.4890; Microsoft Windows 11 10.0.22631.4890; Microsoft Windows 11 10.0.26100.3107; Microsoft Windows Server 2016 10.0.14393.7785; Microsoft Windows Server 2019 10.0.17763.6893; Microsoft Windows Server 2022 10.0.20348.3148; Microsoft Windows Server 2022, 23H2 Edition (Server Core installation) 10.0.25398.1425; Microsoft Windows Server 2025 10.0.26100.3107. Check the vendor advisory for mitigations.

References

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