CVE-2025-54764
📋 TL;DR
CVE-2025-54764 is a timing side-channel vulnerability in Mbed TLS that allows local attackers to potentially extract RSA private keys by measuring execution time differences in certain mathematical operations. This affects systems using vulnerable Mbed TLS versions for RSA operations, particularly in shared environments where attackers have local access. The vulnerability requires local access to the target system.
💻 Affected Systems
- Mbed TLS
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete compromise of RSA private keys, leading to decryption of encrypted communications, impersonation of services, or bypass of authentication mechanisms.
Likely Case
Partial key recovery requiring significant computational resources and repeated measurements, potentially enabling targeted attacks against specific RSA operations.
If Mitigated
Minimal impact if systems use constant-time implementations or are patched, though some residual risk remains from other timing channels.
🎯 Exploit Status
Exploitation requires local access, precise timing measurements, and significant computational resources for key recovery. The attack is not trivial but feasible for determined attackers.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 3.6.5
Vendor Advisory: https://mbed-tls.readthedocs.io/en/latest/security-advisories/mbedtls-security-advisory-2025-10-ssbleed-mstep/
Restart Required: No
Instructions:
1. Download Mbed TLS 3.6.5 or later from official sources. 2. Replace vulnerable library files with patched versions. 3. Recompile any applications linking against Mbed TLS. 4. Test functionality before deployment.
🔧 Temporary Workarounds
Disable RSA operations
allIf RSA is not required, disable RSA cipher suites and operations in your configuration
Configure TLS to use only ECC cipher suites
Disable RSA key exchange in server/client configurations
Use constant-time alternatives
allImplement constant-time RSA operations using alternative libraries or custom implementations
🧯 If You Can't Patch
- Isolate systems using vulnerable Mbed TLS versions from untrusted users
- Implement strict access controls to prevent local attackers from measuring timing differences
🔍 How to Verify
Check if Vulnerable:
Check Mbed TLS version with: mbedtls_version -v or examine library files for version informationCheck Version:
mbedtls_version -vVerify Fix Applied:
Verify version is 3.6.5 or later and test RSA operations with timing analysis tools📡 Detection & Monitoring
Log Indicators:
- Unusual timing patterns in RSA operations
- Multiple failed authentication attempts with timing variations
Network Indicators:
- Unusual local process activity during TLS handshakes
- Suspicious timing measurements from local users
SIEM Query:
Process monitoring for timing measurement tools combined with Mbed TLS process activity