SYSTEM privilege escalation via NTFS buffer overflow
Published Jun 8, 2021 · Updated Jan 12, 2026
Heap buffer overflow in Microsoft Windows NTFS allows local users to gain SYSTEM privileges through a crafted extended-attribute query. NtfsQueryEaUserEaList subtracts alignment padding from the attacker-controlled output length without checking for integer underflow, then copies an extended attribute beyond the kernel heap buffer. Local code execution is required; successful exploitation creates arbitrary kernel memory access and permits SYSTEM-token takeover.
Summary
What happened
Heap buffer overflow in Microsoft Windows NTFS allows local users to gain SYSTEM privileges through a crafted extended-attribute query. NtfsQueryEaUserEaList subtracts alignment padding from the attacker-controlled output length without checking for integer underflow, then copies an extended attribute beyond the kernel heap buffer. Local code execution is required; successful exploitation creates arbitrary kernel memory access and permits SYSTEM-token takeover.
The record
- CVE
- CVE-2021-31956
- Published
- Jun 8, 2021
- Updated
- Jan 12, 2026
- Vendor
- Microsoft
- Product
- Windows 10 Version 1507
- Classifications
- CWE-191, CWE-787, T1068
- Attack vector
- local
- Privileges
- authenticated
Timeline
How it unfolded
- Apr 14, 2021Exploitation reportedPuzzleMaker Chrome and Windows zero-day exploit chain
- Jun 8, 2021CVE publishedPublication date reported by the CVE source.
- Jan 12, 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=10.0.0 <10.0.10240.18967
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
- NCC Group NTFS with WNF proof of conceptproof of concept · demonstrated
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Reported exploitation
- CISA Known Exploited Vulnerabilities listingknown exploited catalog
- PuzzleMaker Chrome and Windows zero-day exploit chainexploit chain
Technologies
Your stack
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Your stack
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