CVE-2026-21250: Windows HTTP.sys Elevation of Privilege Vulnerability

Severity: high (CVSS 7.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.1% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2026-02-10 · updated 2026-08-19
Weakness: CWE-822

Description

Untrusted pointer dereference in Windows HTTP.sys allows an authorized attacker to elevate privileges locally.

Affected products

Microsoft Windows 11: before 10.0.26100.7781 — fixed in 10.0.26100.7781
Microsoft Windows 11 25H2: before 10.0.26200.7781 — fixed in 10.0.26200.7781
Microsoft Windows Server 2022, 23H2 Edition (Server Core installation): before 10.0.25398.2149 — fixed in 10.0.25398.2149
Microsoft Windows Server 2025: before 10.0.26100.32313 — fixed in 10.0.26100.32313
Microsoft Windows 11: from 10.0.26100.0 before 10.0.26100.7840 — fixed in 10.0.26100.7840
Microsoft Windows 11 25H2: from 10.0.26200.0 before 10.0.26200.7840 — fixed in 10.0.26200.7840
Microsoft Windows 11 version 26H1: from 10.0.28000.0 before 10.0.28000.1575 — fixed in 10.0.28000.1575
Microsoft Windows Server 2022, 23H2 Edition (Server Core installation): from 10.0.25398.0 before 10.0.25398.2149 — fixed in 10.0.25398.2149
Microsoft Windows Server 2025: from 10.0.26100.0 before 10.0.26100.32370 — fixed in 10.0.26100.32370

How to fix

Upgrade to a fixed version: Microsoft Windows 11 10.0.26100.7781; Microsoft Windows 11 25H2 10.0.26200.7781; Microsoft Windows Server 2022, 23H2 Edition (Server Core installation) 10.0.25398.2149; Microsoft Windows Server 2025 10.0.26100.32313; Microsoft Windows 11 10.0.26100.7840; Microsoft Windows 11 25H2 10.0.26200.7840; Microsoft Windows 11 version 26H1 10.0.28000.1575; Microsoft Windows Server 2022, 23H2 Edition (Server Core installation) 10.0.25398.2149; Microsoft Windows Server 2025 10.0.26100.32370. Check the vendor advisory for mitigations.

References

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21250

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