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CVE-2026-56389VulnerabilityPublished Updated

GNU Bison · Arbitrary Command Execution

Affects MicrosoftSource GCVE Database

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Authoritative record:CVE-2026-56389· Medium 6.8

Not known to be exploited · CVSS 6.8 Medium.

Data as of 12 Nov 2026, 23:24 UTC

CVSS 4.0 base score
6.8Medium
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.1% chance of exploitation in 30 days – higher than 5% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:A/VC:N/VI:H/VA:L/SC:L/SI:L/SA:L

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 29 Jul 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 13 Nov 2026.

What to do

Affected software

ProductAffectedFixed in
GNUBisonAffected
  • =3.8.2
Fixed in–

AI-suggested

A fix for this vulnerability has been committed by the maintainers. Users should update to a version that includes the fix once it is officially released. Until then, avoid running bison --html on untrusted grammar files to prevent arbitrary code execution. Monitor the official GNU Bison project for updated releases and advisories.

Description

To determine the support lifecycle for your software, see the Microsoft Support Lifecycle: https://support.microsoft.com/lifecycle

References

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