CVE-2026-44699

Name	CVE-2026-44699
Description	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.
Source	CVE (at NVD; CERT, ENISA, LWN, oss-sec, fulldisc, Debian ELTS, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more)
Debian Bugs	1136810

Vulnerable and fixed packages

The table below lists information on source packages.

Source Package	Release	Version	Status
libjwt (PTS)	bullseye	1.10.2-1+deb11u1	fixed
	bookworm	1.10.2-1+deb12u1	fixed
	forky, sid, trixie	1.17.2-1	fixed
libjwt3 (PTS)	forky, sid	3.3.3-1	fixed

The information below is based on the following data on fixed versions.

Package	Type	Release	Fixed Version	Urgency	Origin	Debian Bugs
libjwt	source	(unstable)	(not affected)
libjwt3	source	(unstable)	3.3.3-1			1136810

Notes

- libjwt <not-affected> (Only affects the 3.x series)
https://github.com/benmcollins/libjwt/security/advisories/GHSA-q843-6q5f-w55g
Fixed by: https://github.com/benmcollins/libjwt/commit/49c730a4036c5ae67a4a97e4e55101e445fda694 (v3.3.3)