CVE-2025-52496: Mbed mbedtls · Compiler Optimization Removal or Modification of Security-critical Code
Affects Mbed mbedtlsSource CVE Database V5
Not known to be exploited · CVSS 7.8 High : upgrade to 3.6.4 soon.
Data as of 26 Oct 2026, 10:12 UTC
- EPSS
- 0.2% chance of exploitation in 30 days – higher than 11% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available – fixed in 3.6.4
CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:NExploitation evidence
Disclosed: evidence found.
CVE published 4 Jul 2025
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.
What to do
Upgrade mbed-tls/mbedtls to 3.6.4.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
GitHubmbed-tls/mbedtlspkg:github/mbed-tls/mbedtlsOther threats | Affected
| Fixed in
|
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
AI-suggested
- Upgrade Mbed TLS to version 3.6.4 or later as soon as it becomes available to ensure the race condition and compiler optimization issues are resolved.
- Review and adjust compiler optimization settings to prevent unsafe code removal or modification, particularly in builds involving AESNI detection and cryptographic routines.
- Conduct thorough code audits and testing in multithreaded environments to detect potential race conditions or synchronization issues related to cryptographic operations.
- Limit local access to systems running vulnerable Mbed TLS versions by enforcing strict access controls and monitoring for suspicious activity.
- Implement runtime protections such as memory protection and process isolation to reduce the risk of key extraction.
- 7. For critical systems, consider additional cryptographic layers or hardware security modules (HSMs) to protect key material from software-level vulnerabilities. 8. Educate developers and system administrators about the risks of compiler optimizations affecting security-critical code and encourage secure coding practices.
Description
Mbed TLS before 3.6.4 has a race condition in AESNI detection if certain compiler optimizations occur. An attacker may be able to extract an AES key from a multithreaded program, or perform a GCM forgery.