CVE-2026-27890

Name	CVE-2026-27890
Description	Firebird is an open-source relational database management system. In versions prior to 5.0.4, 4.0.7 and 3.0.14, when processing CNCT_specific_data segments during authentication, the server assumes segments arrive in strictly ascending order. If segments arrive out of order, the Array class's grow() method computes a negative size value, causing a SIGSEGV crash. An unauthenticated attacker who knows only the server's IP and port can exploit this to crash the server. This issue has been fixed in versions 5.0.4, 4.0.7 and 3.0.14.
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)

Vulnerable and fixed packages

The table below lists information on source packages.

Source Package	Release	Version	Status
firebird3.0 (PTS)	bullseye	3.0.7.33374.ds4-2	vulnerable
	bullseye (security)	3.0.7.33374.ds4-2+deb11u1	vulnerable
	bookworm	3.0.11.33637.ds4-2+deb12u1	vulnerable
	trixie	3.0.12.ds7-13+deb13u1	vulnerable
	forky, sid	3.0.13.ds7-2	vulnerable
firebird4.0 (PTS)	trixie (security), trixie	4.0.5.3140.ds6-17+deb13u1	vulnerable
	forky, sid	4.0.6.3221.ds6-2	vulnerable

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

Package	Type	Release	Fixed Version	Urgency	Origin	Debian Bugs
firebird3.0	source	(unstable)	(unfixed)
firebird4.0	source	(unstable)	(unfixed)

https://github.com/FirebirdSQL/firebird/security/advisories/GHSA-6crx-4g37-7j49