CVE-2026-42010

Name	CVE-2026-42010
Description	A flaw was found in gnutls. Servers configured with RSA-PSK (Rivest–Shamir–Adleman – Pre-Shared Key) wrongfully matched usernames containing a NUL character with truncated usernames. A remote attacker could exploit this by sending a specially crafted username, leading to an authentication bypass. This vulnerability allows an attacker to gain unauthorized access by circumventing the authentication process.
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)
References	DSA-6281-1
Debian Bugs	1135319

Vulnerable and fixed packages

The table below lists information on source packages.

Source Package	Release	Version	Status
gnutls28 (PTS)	bullseye	3.7.1-5+deb11u5	vulnerable
	bullseye (security)	3.7.1-5+deb11u9	vulnerable
	bookworm	3.7.9-2+deb12u6	vulnerable
	bookworm (security)	3.7.9-2+deb12u7	fixed
	trixie	3.8.9-3+deb13u3	vulnerable
	trixie (security)	3.8.9-3+deb13u4	fixed
	forky, sid	3.8.13-1	fixed

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

Package	Type	Release	Fixed Version	Origin	Debian Bugs
gnutls28	source	bookworm	3.7.9-2+deb12u7	DSA-6281-1
gnutls28	source	trixie	3.8.9-3+deb13u4	DSA-6281-1
gnutls28	source	(unstable)	3.8.13-1		1135319

Notes

https://www.gnutls.org/security-new.html#GNUTLS-SA-2026-04-29-4
https://gitlab.com/gnutls/gnutls/-/issues/1850
Fixed by: https://gitlab.com/gnutls/gnutls/-/commit/cb1833afd9b6309563211b1c0a7c291f52ca98d5 (3.8.13)