Vulnerability 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.
Related Weaknesses (CWE)
References
- https://cert.pl/en/posts/2026/07/CVE-2026-56389
- https://cgit.git.savannah.gnu.org/cgit/bison.git/
- https://cgit.git.savannah.gnu.org/cgit/bison.git/commit/?id=8d101c19d4d9aaedf83a
FAQ
What is CVE-2026-56390?
CVE-2026-56390 is a documented vulnerability. 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‑suppli...
How severe is CVE-2026-56390?
CVSS scoring is not yet available for CVE-2026-56390. Check NVD for updates.
Is there a patch for CVE-2026-56390?
Check the references section above for vendor advisories and patch information. Review vendor security bulletins for remediation guidance.