Key disclosure and GCM forgery via AESNI race
Published Jul 4, 2025 · Updated Nov 3, 2025
A race condition in Mbed TLS before 3.6.4 allows local users to extract AES keys or forge GCM tags through cache timing. In mbedtls_aesni_has_support(), compiler-reordered stores can mark cached CPU features ready before writing them, sending a second startup thread into table-based AES or GCM. Exploitation requires x86 or amd64 with AESNI, concurrent first use, cache observation, and the ability to suspend the initializing thread.
Summary
What happened
A race condition in Mbed TLS before 3.6.4 allows local users to extract AES keys or forge GCM tags through cache timing. In mbedtls_aesni_has_support(), compiler-reordered stores can mark cached CPU features ready before writing them, sending a second startup thread into table-based AES or GCM. Exploitation requires x86 or amd64 with AESNI, concurrent first use, cache observation, and the ability to suspend the initializing thread.
The record
- CVE
- CVE-2025-52496
- Published
- Jul 4, 2025
- Updated
- Nov 3, 2025
- Vendor
- TrustedFirmware.org
- Product
- Mbed TLS
- Classifications
- CWE-733
- Attack vector
- local
- Privileges
- unauthenticated
Timeline
How it unfolded
- Jul 4, 2025CVE publishedPublication date reported by the CVE source.
- Nov 3, 2025Record 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=0 <3.6.4
What conditions does exploitation require?
What is affected?
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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Technologies
Your stack
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Your stack
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