benmcollins libjwt up to 3.3.2 OpenSSL Backend alg risky encryption

Summaryinfo

A vulnerability labeled as problematic has been found in benmcollins libjwt up to 3.3.2. The impacted element is an unknown function of the component OpenSSL Backend. The manipulation of the argument alg results in risky encryption. This vulnerability is identified as CVE-2026-44699. The attack can be executed remotely. There is not any exploit available. The affected component should be upgraded.

Detailsinfo

A vulnerability, which was classified as critical, was found in benmcollins libjwt up to 3.3.2. Affected is an unknown part of the component OpenSSL Backend. The manipulation of the argument alg with an unknown input leads to a risky encryption vulnerability. CWE is classifying the issue as CWE-327. The product uses a broken or risky cryptographic algorithm or protocol. This is going to have an impact on confidentiality, integrity, and availability. CVE summarizes:

LibJWT is a C JSON Web Token Library. From 3.0.0 to 3.3.2, libjwt accepts an RSA JWK that does not contain an alg parameter as the verification key for an HS256/HS384/HS512 token. In the OpenSSL backend, this causes HMAC verification to run with a zero-length key, so an attacker can forge a valid JWT without knowing any secret or RSA private key. This is an algorithm-confusion authentication bypass. It affects applications that load RSA keys from JWKS where alg is omitted, which is valid JWK syntax and common in real deployments, and then choose the verification algorithm from the JWT header, for example in a kid lookup callback. This vulnerability is fixed in 3.3.3.

The advisory is available at github.com. This vulnerability is traded as CVE-2026-44699 since 05/07/2026. The exploitability is told to be easy. It is possible to launch the attack remotely. The exploitation doesn't require any form of authentication. Technical details are known, but there is no available exploit. This vulnerability is assigned to T1600 by the MITRE ATT&CK project.

Upgrading to version 3.3.3 eliminates this vulnerability.

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Productinfo

Vendor

• benmcollins

Name

• libjwt

Version

• 3.3.0
• 3.3.1
• 3.3.2

Website

• Product: https://github.com/benmcollins/libjwt/

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