SYSTEM privilege escalation via unchecked CLFS block indexes
Published Feb 14, 2023 · Updated Aug 19, 2026
Heap-based buffer overflow in Microsoft's Windows CLFS driver allows local users to gain SYSTEM privileges through a crafted BLF file. ExtendMetadataBlock trusts iExtendBlock and iFlushBlock values after incomplete validation, enabling an out-of-bounds block pointer and arbitrary kernel-memory increment. Low-privileged local code can corrupt kernel objects to build read-and-write primitives and execute with SYSTEM authority.
Summary
What happened
Heap-based buffer overflow in Microsoft's Windows CLFS driver allows local users to gain SYSTEM privileges through a crafted BLF file. ExtendMetadataBlock trusts iExtendBlock and iFlushBlock values after incomplete validation, enabling an out-of-bounds block pointer and arbitrary kernel-memory increment. Low-privileged local code can corrupt kernel objects to build read-and-write primitives and execute with SYSTEM authority.
The record
- CVE
- CVE-2023-23376
- Published
- Feb 14, 2023
- Updated
- Aug 19, 2026
- Vendor
- Microsoft
- Product
- Windows 10 Version 1507
- Classifications
- CWE-122, T1068
- Attack vector
- local
- Privileges
- authenticated
Timeline
How it unfolded
- Feb 14, 2023CVE publishedPublication date reported by the CVE source.
- Aug 19, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=10.0.10240.0 <10.0.10240.19747
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
No public exploit references are available in this record.
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Reported exploitation
- CLFS exploit used by ransomware operatorsransomware
- CISA Known Exploited Vulnerability entryknown exploited catalog
Technologies
Your stack
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Your stack
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