CVE-2026-2636: CWE-159 Improper Handling of Invalid Use of Special Elements in Microsoft Windows OS
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.
CVE-2026-2636: CWE-159 Improper Handling of Invalid Use of Special Elements in Microsoft Windows OS
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.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- Fortra
- Date Reserved
- 2026-02-17T18:49:03.493Z
- Cvss Version
- 3.1
- State
- PUBLISHED
Threat ID: 699f6b2db7ef31ef0b54f063
Added to database: 2/25/2026, 9:35:41 PM
Last updated: 2/26/2026, 9:24:18 AM
Views: 4
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