CVE-2026-34872
Critical
Description
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).
SeverityCritical
CVSS9.1
Exploit probability—
Product
Arm Mbed Tls
PublishedApr 1, 2026
First seenApr 1, 2026
Weakness typeCWE-347CWE-347
How to fix
Update
- arm mbed_tls3.6.6 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| arm mbed_tls | v < 3.6.6 | 3.6.6 |
| arm tf-psa-crypto | 1.0.0 | — |
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