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Description

Time-of-check time-of-use (toctou) race condition in Windows Ancillary Function Driver for WinSock allows an authorized attacker to elevate privileges locally.

PUBLISHED Reserved 2025-12-03 | Published 2026-01-13 | Updated 2026-02-22 | Assigner microsoft




HIGH: 7.8CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C

Problem types

CWE-367: Time-of-check Time-of-use (TOCTOU) Race Condition

Product status

10.0.14393.0 (custom) before 10.0.14393.8783
affected

10.0.17763.0 (custom) before 10.0.17763.8276
affected

10.0.19044.0 (custom) before 10.0.19044.6809
affected

10.0.19045.0 (custom) before 10.0.19045.6809
affected

10.0.22631.0 (custom) before 10.0.22631.6491
affected

10.0.22631.0 (custom) before 10.0.22631.6491
affected

10.0.26100.0 (custom) before 10.0.26100.7623
affected

10.0.26200.0 (custom) before 10.0.26200.7623
affected

6.1.7601.0 (custom) before 6.1.7601.28117
affected

6.1.7601.0 (custom) before 6.1.7601.28117
affected

6.0.6003.0 (custom) before 6.0.6003.23717
affected

6.0.6003.0 (custom) before 6.0.6003.23717
affected

6.2.9200.0 (custom) before 6.2.9200.25868
affected

6.2.9200.0 (custom) before 6.2.9200.25868
affected

6.3.9600.0 (custom) before 6.3.9600.22968
affected

6.3.9600.0 (custom) before 6.3.9600.22968
affected

10.0.14393.0 (custom) before 10.0.14393.8783
affected

10.0.14393.0 (custom) before 10.0.14393.8783
affected

10.0.17763.0 (custom) before 10.0.17763.8276
affected

10.0.17763.0 (custom) before 10.0.17763.8276
affected

10.0.20348.0 (custom) before 10.0.20348.4648
affected

10.0.25398.0 (custom) before 10.0.25398.2092
affected

10.0.26100.0 (custom) before 10.0.26100.32230
affected

10.0.26100.0 (custom) before 10.0.26100.32230
affected

References

msrc.microsoft.com/update-guide/vulnerability/CVE-2026-20831 (Windows Ancillary Function Driver for WinSock Elevation of Privilege Vulnerability) vendor-advisory patch

cve.org (CVE-2026-20831)

nvd.nist.gov (CVE-2026-20831)

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