CVE-2026-2636

Denial of Service in Microsoft OS

State: Published
Severity: 5.5 Medium
Published: Feb 25, 2026
Updated: Feb 26, 2026
Reserved: Feb 17, 2026

Description

This vulnerability is caused by a CWE‑159: "Improper Handling of Invalid Use of Special Elements" weakness, which leads to an unrecoverable inconsistency in the CLFS.sys driver. This condition forces a call to the KeBugCheckEx function, allowing an unprivileged user to trigger a system crash. Microsoft silently fixed this vulnerability in the September 2025 cumulative update for Windows 11 2024 LTSC and Windows Server 2025. Windows 25H2 (released in September) was released with the patch. Windows 1123h2 and earlier versions remain vulnerable.

Scores

CVSS	Score	Vector	Source
3.1	5.5 Medium	CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H	Fortra

Weaknesses

CWE-159 Improper Handling of Invalid Use of Special Elements

Affected Products

Product	Versions
Windows OSMicrosoft	before 25H2Affected 1123h2 and earlierAffected

References

https://www.fortra.com/security/advisories/research/fr-2026-001

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