CVE-2026-56389

MEDIUM CVSS 4.0: 6.8 EPSS 0.15%
Updated Jul 30, 2026
GNU
Parameter Value
CVSS 6.8 (MEDIUM)
Type CWE-78 (OS Command Injection)
Vendor GNU
Public PoC No

GNU Bison allows for an execution of an arbitrary program during HTML report generation due to improper handling of grammar-defined configuration variables. A grammar file can override the executable used for the XML‑to‑HTML transformation step via %define tool.xsltproc, which is accepted without restriction and passed directly to execvp(). When running bison --html on a attacker-provided grammar, this behavior allows execution of an arbitrary program with the privileges of the Bison process.

Maintainers of this project were notified about this vulnerability, and fixed the issue in commit 3169c1e7a2c6acc4c59dfcf8b089896d6881925b. 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.

Attack Parameters

Attack Vector
Local
Requires local access
Attack Complexity
Low
Easy to exploit
Attack Requirements
None
No additional conditions
Privileges Required
None
No privileges needed
User Interaction
Active
User action required

Impact Assessment

Confidentiality
None
No data leak
Integrity
High
Complete data modification
Availability
Low
Partial disruption

CVSS Vector v4.0

Weakness Type (CWE)