# CVE-2026-56389: bison: GNU Bison allows for an execution of an arbitrary program during HTML report generation due to improper handling of g...

CVE-2026-56389 is fixed in bison on 1 platform, first by bison 2:3.8.2+dfsg-1ubuntu0.22.04.1, released July 29, 2026. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2026-56389
- Priority: Routine
- CVSS: n/a (Medium)
- EPSS: 0.0016
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Jul 29, 2026

## Description

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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | bison Ubuntu 22.04.1 LTS (jammy) | 2:3.8.2+dfsg-1ubuntu0.22.04.1 | [bison 2:3.8.2+dfsg-1ubuntu0.22.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-jammy-bison-2-3.8.2-dfsg-1ubuntu0.22.04.1.md) | Jul 29, 2026 |
| Linux | bison Ubuntu 24.04.5 LTS (noble) | 2:3.8.2+dfsg-1ubuntu0.24.04.1 | [bison 2:3.8.2+dfsg-1ubuntu0.24.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-noble-bison-2-3.8.2-dfsg-1ubuntu0.24.04.1.md) | Jul 29, 2026 |
| Linux | bison Ubuntu 26.04.1 LTS (resolute) | 2:3.8.2+dfsg-1ubuntu0.26.04.1 | [bison 2:3.8.2+dfsg-1ubuntu0.26.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-bison-2-3.8.2-dfsg-1ubuntu0.26.04.1.md) | Jul 29, 2026 |

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Data as of 2026-11-09T01:18:40Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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