CVE intelligence

CVE-2026-56389

Vulnerability intelligence

Published Jul 29, 2026Sources checked Oct 28, 2026

8.6HIGHCVSS out of 10

What this means

Review the available evidence

CVE-2026-56389 and is rated High severity with a CVSS score of 8.6. It is not in the current CISA KEV record we collected. That does not prove exploitation has not occurred.

What to do next

Remediation and response

Microsoft Security Response Center guidance

Vendor revision: Oct 22, 2026

CBL-Mariner Releases

Vendor-listed releases

3.8.2-2

CISA KEVNot listedBased on the latest collected catalog

EPSS0.2%Estimated 30-day exploitation probability

Ransomware useNot markedCISA KEV ransomware field

Threat actors0Source-linked actor relationships

Overview

What is CVE-2026-56389?

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.

Source: NVD