CVE-2026-2636
Medium
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.
SeverityMedium
CVSS5.5
Exploit probability—
Product
Windows OS
PublishedFeb 25, 2026
First seenFeb 25, 2026
Weakness typeCWE-159CWE-159
How to fix
Update
- Microsoft Windows OS25H2 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| Microsoft Windows OS | v < 25H2, v ≤ 1123h2 | 25H2 |
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