Critical severity · published Apr 1, 2026
CVE-2026-34872
An issue was discovered in Mbed TLS 3.5.x and 3.6.x through 3.6.5 and TF-PSA-Crypto 1.0
9.1
CVSS
0.2%
EPSS
No
On KEV
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).
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
High
Integrity
High
Availability
None
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.2% · higher than 10% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
MT
Mbed Tls · Arm
before 3.6.6 · source: NVD
TF
Tf-psa-crypto · Arm
1.0.0 · source: NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-34872
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-34872
Vendor Advisory
https://mbed-tls.readthedocs.io/en/latest/security-advisories/
Mitigation
https://mbed-tls.readthedocs.io/en/latest/security-advisories/mbedtls-security-advisory-2026-03-ffdh-peerkey-checks/
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