Windows
CVE-2026-2636
MEDIUM
Vulnerability Assessment
| Weakness |
CWE
OWASP Top 10:2025
A05:2025 - Injection
ASVS 5.0
V1 - Encoding and Sanitization Special element handling
|
| Impact | CVSS 5.5 (MEDIUM). Attack vector: Local. Complexity: Low. Privileges required: Low. User interaction: None. |
| Exploit ScenarioDerived | An attacker could exploit this flaw, an unrecoverable inconsistency in the CLFS. |
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Alert meAnalysisAIv1 – Mar 12, 2026
Local denial of service in Windows CLFS.sys driver allows unprivileged users to crash the system through improper handling of special elements. Affected versions include Windows 11 2024 LTSC and Windows Server 2025 prior to the September 2025 cumulative update, while Windows 25H2 and later contain the patch. No public exploit code is currently available, and the vulnerability carries a CVSS score of 5.5 with zero estimated probability of exploitation.
Earlier versions of this analysis (1)
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. [CVSS 5.5 MEDIUM]
RemediationAI
Monitor vendor advisories for a patch.
Affected ProductsAI
This vulnerability is caused by a CWE‑159: "Improper Handling of Invalid Use of Special Elements" weakness, which leads to an unrecoverable inconsiste
Affects your stack
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Technical ContextAI · show details
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. Window
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- Exploit and PoC references, threat intelligence from 22 sources
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Severity by source
AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Primary rating from NVD · only source for this CVE.
CVSS VectorNVD
DescriptionCVE.org
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.
Executive ViewAI
Organizations using This vulnerability should be aware of moderate risk from CVE-2026-2636 rated CVSS 5.5. Exploitation could compromise the security of affected deployments. Organizations should apply vendor updates when available and monitor for exploitation.
Apply vendor patch. If patching is delayed: restrict network access and enable monitoring.
Threat Intelligence Overview
NVD
CVE.org
EPSS
How this decision was reached
The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.
What every action level means
SSVC AssessmentENISA
Priority Score
Attack Technique
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GitHub PoC
Exploit-DB