Vulnerability 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 Score
CRITICAL
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Arm | Mbed Tls | < 3.6.6 |
| Arm | Tf-Psa-Crypto | 1.0.0 |
Related Weaknesses (CWE)
References
- https://mbed-tls.readthedocs.io/en/latest/security-advisories/Vendor Advisory
- https://mbed-tls.readthedocs.io/en/latest/security-advisories/mbedtls-security-aMitigationVendor Advisory
FAQ
What is CVE-2026-34872?
CVE-2026-34872 is a vulnerability with a CVSS score of 9.1 (CRITICAL). 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-He...
How severe is CVE-2026-34872?
CVE-2026-34872 has been rated CRITICAL with a CVSS base score of 9.1/10. This is considered a critical vulnerability requiring immediate attention.
Is there a patch for CVE-2026-34872?
Check the references section above for vendor advisories and patch information. Affected products include: Arm Mbed Tls, Arm Tf-Psa-Crypto.