CVE-2026-56390
published 2026-07-29CVE-2026-56390: GNU Bison improperly handles grammar‑defined output paths. Grammar directives such as %output and %header allow specifying file paths, which are accepted…
PriorityP429medium6.3CVSS 3.1
AVLACLPRNUIRSCCNIHAN
EPSS
0.13%
2.5th percentile
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.
Affected
2 ranges
| Vendor | Product | Version range | Fixed in |
|---|---|---|---|
| gnu | bison | — | — |
| gnu | bison | — | — |
CVSS provenance
nvdv3.16.3MEDIUMCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:C/C:N/I:H/A:N
nvdv4.04.6MEDIUMCVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:A/VC:N/VI:L/VA:N/SC:N/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
vendor_redhat4.6MEDIUM
Stop checking back — get the weekly exploitation signal.
Every Monday: what got weaponized or added to CISA KEV in the last seven days — each CVE cross-linked to its PoC, Nuclei template, and detection rule. Free, one email a week, unsubscribe in one click.
Red Hat
bison: GNU Bison: Arbitrary file overwrite via grammar-defined output paths
vendor_redhat·2026-07-29·CVSS 4.6
CVE-2026-56390 [MEDIUM] CWE-22 bison: GNU Bison: Arbitrary file overwrite via grammar-defined output paths
bison: GNU Bison: Arbitrary file overwrite via grammar-defined output paths
A flaw was found in GNU Bison. When processing attacker-supplied grammar, the software improperly handles grammar-defined output paths. This allows an attacker to use directives such as %output and %header to specify arbitrary file paths. Consequently, generated files can be directed to any writable location on the filesystem, potentially overwriting existing files and leading to data integrity issues.
Package: bison (Red Hat Enterprise Linux 10) - Fix deferred
Package: bison (Red Hat Enterprise Linux 6) - Out of support scope
Package: bison (Red Hat Enterprise Linux 7) - Fix deferred
Package: bison (Red Hat Enterprise Linux 8) - Fix deferred
Package: bison (Red Hat Enterprise Linux 9) - Fix deferred
Package
GHSA
GNU Bison improperly handles grammar‑defined output paths.
ghsa_unreviewed·2026-07-29
CVE-2026-56390 [MEDIUM] CWE-73 GNU Bison improperly handles grammar‑defined output paths.
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.
No detection rules found.
No public exploits indexed.
Bugzilla
CVE-2026-56390 bison: GNU Bison: Arbitrary file overwrite via grammar-defined output paths [fedora-all]
bugzilla·2026-07-30·CVSS 4.6
CVE-2026-56390 [MEDIUM] CVE-2026-56390 bison: GNU Bison: Arbitrary file overwrite via grammar-defined output paths [fedora-all]
CVE-2026-56390 bison: GNU Bison: Arbitrary file overwrite via grammar-defined output paths [fedora-all]
Disclaimer: Community trackers are created by Red Hat Product Security team on a best effort basis. Package maintainers are required to ascertain if the flaw indeed affects their package, before starting the update process.
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 noti
Bugzilla
CVE-2026-56390 bison: GNU Bison: Arbitrary file overwrite via grammar-defined output paths
bugzilla·2026-07-29·CVSS 4.6
CVE-2026-56390 [MEDIUM] CVE-2026-56390 bison: GNU Bison: Arbitrary file overwrite via grammar-defined output paths
CVE-2026-56390 bison: GNU Bison: Arbitrary file overwrite via grammar-defined output paths
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 t
2026-07-29
Published