CVE-2026-21253

Published: Feb 10, 2026Modified: Mar 27, 2026

7.0

Vector

CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H

Exploitability: 1.0 / Impact: 5.9

Source: secure@microsoft.com (Secondary)

Description

Use after free in Mailslot File System allows an authorized attacker to elevate privileges locally.

Affected (23)

Products: Microsoft: Windows 10 1607, Windows 10 1809, Windows 10 21h2, Windows 10 22h2, Windows 11 23h2, Windows 11 24h2, Windows 11 25h2, Windows Server 2012, Windows Server 2016, Windows Server 2019, Windows Server 2022, Windows Server 2022 23h2, Windows Server 2025

13 products

Windows 10 1607

Windows 10 1809

Windows 10 21h2

Windows 10 22h2

Windows 11 23h2

Windows 11 24h2

Windows 11 25h2

Windows Server 2012

Windows Server 2016

Windows Server 2019

Windows Server 2022

Windows Server 2022 23h2

Windows Server 2025

Configuration A

23 vulnerable

Vulnerable Software	Affected Versions
Microsoft Windows 10 1607	Before 10.0.14393.8868
Microsoft Windows 10 1607	Before 10.0.14393.8868
Microsoft Windows 10 1809	Before 10.0.17763.8389
Microsoft Windows 10 1809	Before 10.0.17763.8389
Microsoft Windows 10 21h2	Before 10.0.19044.6937
Microsoft Windows 10 21h2	Before 10.0.19044.6937
Microsoft Windows 10 21h2	Before 10.0.19044.6937
Microsoft Windows 10 22h2	Before 10.0.19045.6937
Microsoft Windows 10 22h2	Before 10.0.19045.6937
Microsoft Windows 10 22h2	Before 10.0.19045.6937
Microsoft Windows 11 23h2	Before 10.0.22631.6649
Microsoft Windows 11 23h2	Before 10.0.22631.6649
Microsoft Windows 11 24h2	Before 10.0.26100.7781
Microsoft Windows 11 24h2	Before 10.0.26100.7781
Microsoft Windows 11 25h2	Before 10.0.26200.7781
Microsoft Windows 11 25h2	Before 10.0.26200.7781
Microsoft Windows Server 2012	All versions
Microsoft Windows Server 2012	Version r2
Microsoft Windows Server 2016	Before 10.0.14393.8868
Microsoft Windows Server 2019	Before 10.0.17763.8389
Microsoft Windows Server 2022	Before 10.0.20348.4711
Microsoft Windows Server 2022 23h2	Before 10.0.25398.2149
Microsoft Windows Server 2025	Before 10.0.26100.32313

Related CWEs

The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.

References (3)

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21253

Source: secure@microsoft.com

Vendor Advisory

https://www.vicarius.io/vsociety/posts/cve-2026-21253-detection-script-elevation-of-privilege-vulnerability-in-mailslot-file-system

Source: af854a3a-2127-422b-91ae-364da2661108

https://www.vicarius.io/vsociety/posts/cve-2026-21253-mitigation-script-elevation-of-privilege-vulnerability-in-mailslot-file-system

Source: af854a3a-2127-422b-91ae-364da2661108

Timeline

No history available yet.