Use of insufficiently random values in mbed TLS - CVE-2026-25835

Detailed vulnerability description

The vulnerability allows a local user to obtain predictable random numbers.

The vulnerability exists due to insufficient randomness in the PSA random generator when application state is cloned. A local user can exploit system or application cloning scenarios such as fork(), VM cloning, or hibernation resume to cause multiple instances to generate identical random outputs, enabling prediction of cryptographic keys and nonces.

Applications that use the PSA random generator are affected when the system or application state is cloned without reseeding the generator. This includes scenarios such as fork() on Unix-like systems, virtual machine cloning, and resuming hibernation images multiple times.

How to mitigate CVE-2026-25835

Sources

• https://mbed-tls.readthedocs.io/en/latest/security-advisories/mbedtls-security-advisory-2026-03-rng-cloning/
• https://mbed-tls.readthedocs.io/en/latest/kb/how-to/random_generator_cloning/