GNU Bison · Arbitrary Command Execution
Affects MicrosoftSource GCVE Database
Not known to be exploited · CVSS 6.8 Medium.
Data as of 12 Nov 2026, 23:24 UTC
- 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:LExploitation evidence
Disclosed: evidence found.
CVE published 29 Jul 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by 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
| Product | Affected | Fixed in |
|---|---|---|
| GNUBison | Affected
| 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
- msrc.microsoft.com/csaf/vex/2026/msrc_cve-2026-56389.json (opens in a new tab)
- support.microsoft.com/lifecycle (opens in a new tab)
- first.org/cvss (opens in a new tab)
- ubuntu.com/security/CVE-2026-56389 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2026-56389 (opens in a new tab)
- cert.pl/en/posts/2026/07/CVE-2026-56389 (opens in a new tab)
- cgit.git.savannah.gnu.org/cgit/bison.git/commit/?id=3169c1e7a2c6acc4c59dfcf8b089896d6881925b (opens in a new tab)
- cgit.git.savannah.gnu.org/cgit/bison.git/ (opens in a new tab)