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VulnerabilityPublished Updated

CVE-2025-52496: Mbed mbedtls · Compiler Optimization Removal or Modification of Security-critical Code

Affects Mbed mbedtlsSource CVE Database V5

0

Not known to be exploited · CVSS 7.8 High : upgrade to 3.6.4 soon.

Data as of 26 Oct 2026, 10:12 UTC

CVSS 3.1 base score
7.8High
How severe the flaw is on the 0–10 CVSS scale.
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:N

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 4 Jul 2025

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponised: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq 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

ProductAffectedFixed in
GitHubmbed-tls/mbedtlspkg:github/mbed-tls/mbedtlsOther threatsAffected
  • <3.6.4
Fixed in
  • 3.6.4

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

  1. 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.
  2. Review and adjust compiler optimization settings to prevent unsafe code removal or modification, particularly in builds involving AESNI detection and cryptographic routines.
  3. Conduct thorough code audits and testing in multithreaded environments to detect potential race conditions or synchronization issues related to cryptographic operations.
  4. Limit local access to systems running vulnerable Mbed TLS versions by enforcing strict access controls and monitoring for suspicious activity.
  5. Implement runtime protections such as memory protection and process isolation to reduce the risk of key extraction.
  6. 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.

References

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