CVE-2026-2636
Improper Handling in CLFS.sys Causes Windows System Crash
Publication date: 2026-02-25
Last updated on: 2026-02-25
Assigner: Fortra
Description
Description
CVSS Scores
EPSS Scores
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Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| microsoft | windows_server | to 2025 (exc) |
| microsoft | windows | From 2025-09 (inc) |
| microsoft | windows_server | From 2025-09 (inc) |
| microsoft | windows | to 2025-09 (exc) |
| microsoft | windows | to 2025 (inc) |
| microsoft | windows_server | to 2025 (inc) |
| microsoft | windows | 11 |
| microsoft | windows | to 2025 (exc) |
Helpful Resources
Exploitability
| CWE ID | Description |
|---|---|
| CWE-159 | The product does not properly filter, remove, quote, or otherwise manage the invalid use of special elements in user-controlled input, which could cause adverse effect on its behavior and integrity. |
Attack-Flow Graph
AI Powered Q&A
Can you explain this vulnerability to me?
This vulnerability is caused by a weakness classified as CWE-159, which involves improper handling of invalid use of special elements. Specifically, it leads to an unrecoverable inconsistency in the CLFS.sys driver, a component in Microsoft Windows.
This inconsistency forces the system to call the KeBugCheckEx function, which triggers a system crash (commonly known as a Blue Screen of Death).
An unprivileged user can exploit this vulnerability to cause the system to crash.
How can this vulnerability impact me? :
The primary impact of this vulnerability is that an unprivileged user can cause a system crash by exploiting the flaw in the CLFS.sys driver.
This results in a denial of service condition, where the affected system becomes unavailable until it is restarted.
There is no indication that this vulnerability allows for data theft or privilege escalation, but the disruption caused by system crashes can affect availability and reliability.
How does this vulnerability affect compliance with common standards and regulations (like GDPR, HIPAA)?:
I don't know
How can this vulnerability be detected on my network or system? Can you suggest some commands?
I don't know
What immediate steps should I take to mitigate this vulnerability?
To mitigate this vulnerability, apply the September 2025 cumulative update for Windows 11 2024 LTSC and Windows Server 2025, or upgrade to Windows 25H2 or later versions which include the patch.
Systems running Windows 1123h2 and earlier versions remain vulnerable and should be updated as soon as possible.