CVE-2026-56390

Name	CVE-2026-56390
Description	GNU Bison improperly handles grammar‑defined output paths. Grammar directives such as %output and %header allow specifying file paths, which are accepted without restriction and override caller‑supplied output options. When processing attacker-supplied grammar, this behavior allows directing generated files to arbitrary writable locations on the filesystem, potentially overwriting existing files accessible to the Bison process. Maintainers of this project were notified about this vulnerability, and fixed the issue in commit 8d101c19d4d9aaedf83a448c925513742d4efcf0. However, they did not provide vulnerable version range. Version 3.8.2 was tested and confirmed as vulnerable, other versions were not tested but might also be vulnerable.
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	1143158

Vulnerable and fixed packages

The table below lists information on source packages.

Source Package	Release	Version	Status
bison (PTS)	bullseye	2:3.7.5+dfsg-1	vulnerable
	forky, sid, bookworm, trixie	2:3.8.2+dfsg-1	vulnerable

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

Package	Type	Release	Fixed Version	Urgency	Origin	Debian Bugs
bison	source	(unstable)	(unfixed)			1143158

Notes

[trixie] - bison <no-dsa> (Minor issue)
[bookworm] - bison <postponed> (Minor issue)
[bullseye] - bison <postponed> (Minor issue)
https://cert.pl/en/posts/2026/07/CVE-2026-56389/
https://cgit.git.savannah.gnu.org/cgit/bison.git/commit/?id=8d101c19d4d9aaedf83a448c925513742d4efcf0