mbedtls: An issue was discovered in Mbed TLS 3.5.x and 3.6.x through 3.6.5 and TF-PSA-Crypto 1.0
CVE-2026-34872 is fixed in mbedtls on 1 platform, first by DEBIAN-CVE-2026-34872, released April 1, 2026. It is not reported as exploited. Patch Radar priority: Urgent.
An issue was discovered in Mbed TLS 3.5.x and 3.6.x through 3.6.5 and TF-PSA-Crypto 1.0. There is a lack of contributory behavior in FFDH due to improper input validation. Using finite-field Diffie-Hellman, the other party can force the shared secret into a small set of values (lack of contributory behavior). This is a problem for protocols that depend on contributory behavior (which is not the case for TLS). The attack can be carried by the peer, or depending on the protocol by an active network attacker (person in the middle).
Where it's fixed
| Product | Fixed in | Fix | Released |
|---|---|---|---|
| Linux | |||
| mbedtls · Debian 13.5 (trixie) | 3.6.6-0.1~deb13u1 | DEBIAN-CVE-2026-34872 | Apr 1, 2026 |
| mbedtls · Debian 14 | 3.6.6-0.1 | DEBIAN-CVE-2026-34872 | Apr 1, 2026 |
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