CVE-2026-3833

Name	CVE-2026-3833
Description	A flaw was found in gnutls. This vulnerability occurs because gnutls performs case-sensitive comparisons of `nameConstraints` labels, specifically for `dNSName` (DNS) or `rfc822Name` (email) constraints within `excludedSubtrees` or `permittedSubtrees`. A remote attacker can exploit this by crafting a leaf certificate with casing differences in the Subject Alternative Name (SAN), leading to a policy bypass where a certificate that should be rejected is instead accepted. This could result in unauthorized access or information disclosure.
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-2026-04-29-5
https://gitlab.com/gnutls/gnutls/-/work_items/1223
https://gitlab.com/gnutls/gnutls/-/issues/1803
https://gitlab.com/gnutls/gnutls/-/issues/1852
Fixed by: https://gitlab.com/gnutls/gnutls/-/commit/19f6508647bdcd3ce21130201e484d7ca6d962c5 (3.8.13)