CVE-2025-66442: Arm Mbed TLS

Medium severity, CVSS 5.1. EPSS: 0.3% chance of exploitation in the next 30 days.

In Mbed TLS through 4.0.0, there is a compiler-induced timing side channel (in RSA and CBC/ECB decryption) that only occurs with LLVM's select-optimize feature. TF-PSA-Crypto through 1.0.0 is also affected.

Affected products

• Arm Mbed TLS: up to and including 4.0.0
• Arm Tf-Psa-Crypto: up to and including 1.0.0

Published 2026-04-01. Last modified 2026-06-17.