Summaryinfo

A vulnerability marked as problematic has been reported in mbed TLS up to 3.6.5. The impacted element is an unknown function of the component FFDH Handler. This manipulation causes entropy. This vulnerability is tracked as CVE-2026-34872. The attack is possible to be carried out remotely. No exploit exists.

Detailsinfo

A vulnerability has been found in mbed TLS up to 3.6.5 and classified as problematic. Affected by this vulnerability is an unknown code of the component FFDH Handler. The manipulation with an unknown input leads to a entropy vulnerability. The CWE definition for the vulnerability is CWE-331. The product uses an algorithm or scheme that produces insufficient entropy, leaving patterns or clusters of values that are more likely to occur than others. As an impact it is known to affect confidentiality. The summary by CVE is:

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).

The advisory is shared at mbed-tls.readthedocs.io. This vulnerability is known as CVE-2026-34872 since 03/31/2026. The exploitation appears to be difficult. The attack can be launched remotely. The exploitation doesn't need any form of authentication. Neither technical details nor an exploit are publicly available. MITRE ATT&CK project uses the attack technique T1600.001 for this issue.

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2026-18021). If you want to get the best quality for vulnerability data then you always have to consider VulDB.

Productinfo

Name

• mbed TLS

Version

• 3.6.0
• 3.6.1
• 3.6.2
• 3.6.3
• 3.6.4
• 3.6.5

CPE 2.3info

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CPE 2.2info

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If you want to get the best quality for vulnerability data then you always have to consider VulDB.

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