Improper input validation in mbed TLS - CVE-2026-34872
Published: April 2, 2026
Vulnerability identifier: #VU124805
CSH Severity: Medium
CVSS v4: 6.9 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-34872
CWE-ID: CWE-20
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to force the FFDH shared secret into a small set of values.
The vulnerability exists due to improper input validation in the FFDH key agreement component when processing a peer's public key during key agreement using PSA_ALG_FFDH. A remote attacker can send a specially crafted public key to force the FFDH shared secret into a small set of values.
Applications are only affected if they use the PSA API to perform FFDH as part of a larger protocol that expects contributory behaviour from FFDH. TLS 1.2 and TLS 1.3 are not affected due to protocol-level protections.
Affected software
mbed TLS
TF-PSA-Crypto
Fedora
mbedtls
TF-PSA-Crypto
Fedora
mbedtls
How to mitigate CVE-2026-34872
Install security update from vendor's website.
mbed TLS - update to 3.6.6
TF-PSA-Crypto - update to 1.1.0
mbedtls - addressed in versions 3.6.6-1.el10_1, 3.6.6-1.el10_2, 3.6.6-1.el10_3
TF-PSA-Crypto - update to 1.1.0
mbedtls - addressed in versions 3.6.6-1.el10_1, 3.6.6-1.el10_2, 3.6.6-1.el10_3