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Description

Time-of-check time-of-use (toctou) race condition in Windows HTTP.sys allows an authorized attacker to elevate privileges locally.

PUBLISHED Reserved 2025-12-11 | Published 2026-02-10 | Updated 2026-02-23 | 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

10.0.17763.0 (custom) before 10.0.17763.8389
affected

10.0.19044.0 (custom) before 10.0.19044.6937
affected

10.0.19045.0 (custom) before 10.0.19045.6937
affected

10.0.22631.0 (custom) before 10.0.22631.6649
affected

10.0.22631.0 (custom) before 10.0.22631.6649
affected

10.0.26100.0 (custom) before 10.0.26100.7840
affected

10.0.26200.0 (custom) before 10.0.26200.7840
affected

10.0.28000.0 (custom) before 10.0.28000.1575
affected

10.0.28000.0 (custom) before 10.0.28000.1575
affected

10.0.17763.0 (custom) before 10.0.17763.8389
affected

10.0.17763.0 (custom) before 10.0.17763.8389
affected

10.0.20348.0 (custom) before 10.0.20348.4773
affected

10.0.25398.0 (custom) before 10.0.25398.2149
affected

10.0.26100.0 (custom) before 10.0.26100.32370
affected

10.0.26100.0 (custom) before 10.0.26100.32370
affected

References

msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21240 (Windows HTTP.sys Elevation of Privilege Vulnerability) vendor-advisory patch

cve.org (CVE-2026-21240)

nvd.nist.gov (CVE-2026-21240)

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