CVE-2025-52496
📋 TL;DR
Mbed TLS versions before 3.6.4 have a race condition in AESNI detection that can occur with certain compiler optimizations. This vulnerability allows attackers to extract AES keys from multithreaded programs or perform GCM forgeries. Affected systems include any application using vulnerable Mbed TLS versions with AES-GCM or AES-CBC encryption in multithreaded environments.
💻 Affected Systems
- Mbed TLS
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Full compromise of AES encryption keys leading to decryption of sensitive data and authentication bypass via GCM forgery attacks.
Likely Case
Partial key extraction enabling limited data decryption or successful GCM forgeries in targeted attacks against vulnerable multithreaded applications.
If Mitigated
No impact if patched or if applications don't use multithreaded AES operations with compiler optimizations enabled.
🎯 Exploit Status
Exploitation requires attacker to trigger the race condition in multithreaded environments with specific compiler optimizations.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 3.6.4
Vendor Advisory: https://github.com/Mbed-TLS/mbedtls-docs/blob/main/security-advisories/mbedtls-security-advisory-2025-06-1.md
Restart Required: Yes
Instructions:
1. Download Mbed TLS 3.6.4 or later from official repository. 2. Replace existing Mbed TLS installation. 3. Recompile any applications using Mbed TLS. 4. Restart affected services.
🔧 Temporary Workarounds
Disable compiler optimizations
allCompile Mbed TLS without optimizations that could trigger the race condition
CFLAGS="-O0" make
Disable AESNI support
linuxForce Mbed TLS to use software AES implementation instead of hardware acceleration
./configure --disable-aesni
make clean && make
🧯 If You Can't Patch
- Isolate vulnerable systems from untrusted networks
- Monitor for unusual cryptographic operations or authentication failures
🔍 How to Verify
Check if Vulnerable:
Check Mbed TLS version with: mbedtls_version -v or examine library files for version < 3.6.4Check Version:
mbedtls_version -v 2>/dev/null || strings /path/to/libmbedtls* | grep -i versionVerify Fix Applied:
Verify version is 3.6.4 or later and test AES-GCM operations in multithreaded environment📡 Detection & Monitoring
Log Indicators:
- Multiple authentication failures with GCM
- Unexpected cryptographic errors in multithreaded contexts
Network Indicators:
- Repeated failed TLS handshakes with AES-GCM ciphers
SIEM Query:
source="application_logs" AND ("AES" OR "GCM") AND ("error" OR "failure" OR "race")