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TI-2026-40749 Aliases CVE-2026-56389GHSA-735p-4prj-f62v

Arbitrary Command Execution in GNU Bison

Priority LOW 29CWE-78Published · Updated

Key facts

Attack vector
Local
Privileges required
None
User interaction
Active
Attack complexity
Low
Attack requirements
None
Impact type
Code execution
Confidentiality · integrity · availability
None · High · Low
Fix status
Deferred Red Hat: fix deferred

Attack profile from CVSS 4.0 · CNA. Fix status from CNA and Red Hat. Impact type from CWE-78.

Summary

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.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00158 5th percentileScored 2026-11-07
Fix Deferred Red Hat: fix deferred

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
No
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
GNUBison3.8.2—No fix listedCNA
  • Bison VendorGNU Affected 3.8.2 Fixed in — No fix listed CNA

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:gnu:bison:3.8.2:*:*:*:*:*:*:*3.8.2VulnerableGNU
  • cpe:2.3:a:gnu:bison:3.8.2:*:*:*:*:*:*:* Versions 3.8.2 Vulnerable ·GNU

Remediation

No fixed version listed by the sources yet.

Vendor assessments

Red Hat

Red Hat rating: Moderate. Red Hat's page for this CVE →

ProductStatusPlan or fix
Red Hat Enterprise Linux 10AffectedNo fix yet: Fix deferred
Red Hat Enterprise Linux 6AffectedNo fix planned: Out of support scope
Red Hat Enterprise Linux 7AffectedNo fix yet: Fix deferred
Red Hat Enterprise Linux 8AffectedNo fix yet: Fix deferred
Red Hat Enterprise Linux 9AffectedNo fix yet: Fix deferred
Red Hat OpenShift Container Platform 4AffectedNo fix yet: Fix deferred
Red Hat OpenShift Container Platform 5AffectedNo fix yet: Fix deferred
Not affected: 1 product
  • Red Hat OpenShift Container Platform 4

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-56389
  2. 2026-10-03 Alias added: GHSA-735p-4prj-f62v
  3. 2026-11-06 Affected versions changed · Red Hat

References

Patch 1

Advisory 1

Other 1

  • TI-2020-14854 GNU Bison before 3.7.1 has a use-after-free in _obstack_free in lib/obstack.c (called… CVSS 3.1MEDIUM 5.5
  • TI-2020-11078 GNU Bison before 3.5.4 allows attackers to cause a denial of service (application crash). CVSS 3.1MEDIUM 5.5
  • TI-2026-40750 Arbitrary Output Location Change in GNU Bison CVSS 4.0MEDIUM 4.6

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences