CVE-2026-2636CWE-159

Denial of Service in Microsoft OS

Medium · published February 25, 2026

CVSS v3.1
5.5
EPSS
0%
Percentile
34.2
In the wild
Unconfirmed
What it is

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.

The record
Technical detail
CVSS v3.1
5.5 · MEDIUM
Vector
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
CVSS v4.0
Not supplied
EPSS
0.00410 · 34.2th percentile
Weakness
CWE-159 · Improper Handling of Invalid Use of Special Elements
Published
2026-02-25T18:57Z
EPSS history
Timeline
  • 25 FEB 18:57Z
    Denial of Service in Microsoft OS
    cvelistv5