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CVE-2026-25834 Trustedfirmware CVE debrief

CVE-2026-25834 is a vulnerability in Mbed TLS, a cryptographic library developed by Trustedfirmware. The vulnerability, with a CVSS score of 6.5 and a severity of MEDIUM, allows for Algorithm Downgrade attacks. This type of attack can occur when a vulnerable system accepts a weaker cryptographic algorithm than it is capable of supporting, potentially leading to a compromise of the system's security. The vulnerability affects Mbed TLS versions 3.3.0 up to 3.6.5 and 4.0.0.

Vendor
Trustedfirmware
Product
Mbed TLS
CVSS
MEDIUM 6.5
CISA KEV
Not listed in stored evidence
Original CVE published
2026-04-01
Original CVE updated
2026-06-05
Advisory published
2026-04-01
Advisory updated
2026-06-05

Who should care

Developers and users of Mbed TLS, especially those using versions 3.3.0 to 3.6.5 and 4.0.0, should be aware of this vulnerability. It is crucial for them to update to a non-vulnerable version to prevent potential Algorithm Downgrade attacks.

Technical summary

The vulnerability is caused by Mbed TLS's improper handling of cryptographic algorithms, allowing an attacker to downgrade the algorithm used for secure communication. This could lead to a loss of confidentiality and integrity of the data being transmitted.

Defensive priority

MEDIUM

Recommended defensive actions

  • Update Mbed TLS to a version that is not vulnerable (e.g., 3.6.6 or later, or a patched version of 4.0.0).

Evidence notes

The CVE was published on 2026-04-01 and modified on 2026-06-05. The vulnerability has been analyzed and verified by official sources.

Official resources

CVE-2026-25834 was published on 2026-04-01 and modified on 2026-06-05.