CVE-2026-34871 Details

A vulnerability exists in Mbed TLS versions prior to 3.6.6, in Mbed TLS 4.x prior to 4.1.0, and in TF-PSA-Crypto versions prior to 1.1.0. The issue arises because the libraries can fall back to using `/dev/urandom` for entropy on Linux systems, which may lead to predictable random data being used in cryptographic operations. This is particularly problematic on embedded devices without hardware random generators, where `/dev/urandom` can return predictable data early in the boot process or during OS installation.

Users should upgrade to Mbed TLS 3.6.6 or a later 3.6.x version, or to TF-PSA-Crypto 1.1.0 or above. In these versions, the library uses `/dev/random` if `getrandom()` is unavailable, which is safer, although it may block on older Linux kernels. For Mbed TLS, package maintainers can revert to `/dev/urandom` by setting the `MBEDTLS_PLATFORM_DEV_RANDOM` option. Applications may also adjust the `mbedtls_platform_dev_random` variable to override the default setting.