What is the CVSS score of EUVD-2026-18021?

EUVD-2026-18021 has a CVSS 3.1 base score of 9.1 (Critical). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N. EPSS exploitation probability: 0.0%.

Is there a patch available for EUVD-2026-18021?

Yes, a patch is available for EUVD-2026-18021. Update the affected software to the latest version immediately.

Jwt Attack EUVD-2026-18021

| CVE-2026-34872 CRITICAL

Improper Verification of Cryptographic Signature (CWE-347)

2026-04-01 mitre

GHSA-347r-37hj-5jc9

Information Disclosure Jwt Attack Red Hat Suse

9.1

CVSS 3.1 · NVD

Severity by source

NVD PRIMARY

9.1 CRITICAL

AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

SUSE

CRITICAL

qualitative

Red Hat

7.5 HIGH

qualitative

Primary rating from NVD.

CVSS VectorNVD

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

None

Lifecycle Timeline

EUVD ID Assigned

Apr 01, 2026 - 19:45 euvd

EUVD-2026-18021

Analysis Generated

Apr 01, 2026 - 19:45 vuln.today

CVE Published

Apr 01, 2026 - 00:00 nvd

CRITICAL 9.1

DescriptionCVE.org

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).

AnalysisAI

Finite-field Diffie-Hellman (FFDH) in Mbed TLS 3.5.x, 3.6.0 through 3.6.5, and TF-PSA-Crypto 1.0 lacks contributory behavior due to improper validation of peer-supplied parameters, allowing an attacker to restrict the shared secret to a small set of predictable values. While the vulnerability does not directly impact TLS (which does not depend on contributory behavior), it poses a significant risk to protocols that do rely on this property, including those where an active network attacker or malicious peer can exploit the weakness. No CVSS score or public exploit code has been assigned at the time of analysis.

Technical ContextAI

Finite-field Diffie-Hellman (FFDH) is a key agreement protocol used in cryptographic systems to establish shared secrets between two parties. Contributory behavior in FFDH ensures that both parties contribute equally to the final shared secret, preventing a malicious peer from forcing the result into a pre-determined or restricted set of values. The vulnerability stems from improper input validation of peer-supplied Diffie-Hellman parameters, allowing an attacker to provide specially crafted values that cause the computed shared secret to collapse into a small subgroup. This is a parameter validation flaw (related to CWE-347 Improper Verification of Cryptographic Signature or similar input validation weaknesses) that undermines the security assumptions of protocols depending on contributory behavior for forward secrecy or session key independence.

RemediationAI

Upgrade Mbed TLS to version 3.6.6 or later, which includes corrected peer-supplied parameter validation for FFDH. Users of TF-PSA-Crypto should upgrade to the patched release addressing this advisory. Organizations unable to upgrade immediately should implement protocol-level mitigations if their use case depends on contributory behavior-such as adding additional validation of the peer's public parameters or using alternative key agreement schemes (e.g., ECDH) that are not affected. Consult the official Mbed TLS security advisory at https://mbed-tls.readthedocs.io/en/latest/security-advisories/mbedtls-security-advisory-2026-03-ffdh-peerkey-checks/ for detailed guidance and confirmation of patched versions.