CVE-2026-2636

Published Feb 25, 2026·Updated Jun 17, 2026

NVD 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.

Public Exploits & PoCs1 found

PoC: CVE-2026-2636_PoC

**CVE-2026-2636** is a vulnerability in the Windows Common Log File System (CLFS) driver (`CLFS.sys`). An unprivileged user can trigger an unrecoverable system state by calling the `ReadFile` API on a handle opened via `CreateLogFile`. This results in a Blue Screen of Death (BSoD), leading to a denial of service (DoS)

CVSS Vector

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

References

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