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5.5
Windows Drivers Can Crash from Invalid Input
CVE-2026-2636
Summary
A bug in the Windows CLFS.sys driver can cause a system crash if the driver receives invalid input. This can happen if an attacker sends malicious data, potentially disrupting system operation. If you're using Windows 11 2024 LTSC or Windows Server 2025, you're already protected. For other affected versions, apply the September 2025 cumulative update when it becomes available.
Original title
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 forc...
Original 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.
nvd CVSS3.1
5.5
Vulnerability type
CWE-159
Published: 25 Feb 2026 · Updated: 12 Mar 2026 · First seen: 6 Mar 2026