Authenticated code execution via event-log backup race
Published May 13, 2025 · Updated Feb 26, 2026
A TOCTOU race in Microsoft Windows MS-EVEN allows remote authenticated users to execute code by controlling an event-log backup source. ElfrOpenBELW validates an EVTX header from an attacker-controlled SMB file, but ElfrBackupELFW later rereads and copies the replaced contents without revalidation. Low-privileged credentials and a writable destination are required; the resulting arbitrary file write can execute code at user logon or through DLL loading.
Summary
What happened
A TOCTOU race in Microsoft Windows MS-EVEN allows remote authenticated users to execute code by controlling an event-log backup source. ElfrOpenBELW validates an EVTX header from an attacker-controlled SMB file, but ElfrBackupELFW later rereads and copies the replaced contents without revalidation. Low-privileged credentials and a writable destination are required; the resulting arbitrary file write can execute code at user logon or through DLL loading.
The record
- CVE
- CVE-2025-29969
- Published
- May 13, 2025
- Updated
- Feb 26, 2026
- Vendor
- Microsoft
- Product
- Windows 10 Version 1507
- Classifications
- CWE-367, T1210
- Attack vector
- network
- Privileges
- authenticated
Timeline
How it unfolded
- May 13, 2025CVE publishedPublication date reported by the CVE source.
- Feb 26, 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 <10.0.10240.21014
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
- EventLogin CVE-2025-29969 proof of conceptfunctional · demonstrated
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Technologies
Your stack
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Your stack
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