CVE-2026-56389

MEDIUMPre-NVD 6.86.8
EchelonGraph scoreLOW confidence

This medium-severity CVE scores 6.8 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit-prediction score not yet available (the EPSS model rescores nightly; freshly-published CVEs typically appear within 48 hours). GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: secondary
Trending — 3 sources updated this week
6.8EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: —CVSS: 6.8Exploit: None knownExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

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.

CVSS v3
6.8
EG Score
6.8(low)
EG Risk
31(Track)
EG Risk 31/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity68% × 45%
Exploitation0% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
—
EPSS %ILE
—
KEV
Not listed

Published

July 29, 2026

Last Modified

July 29, 2026

Advisory Details (2)

Auto-updated Jul 29, 2026
No patch confirmed yet.
generic

bison.git - GNU bison (git mirror)

https://cgit.git.savannah.gnu.org/cgit/bison.git/
generic

Vulnerabilities in GNU Bison software | CERT Polska

https://cert.pl/en/posts/2026/07/CVE-2026-56389

Vendor Advisories for CVE-2026-56389(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 7× in last 7d / 7× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-07-29 13:38 UTCEG score recompute
  2. 2026-07-29 13:38 UTCGHSA enrichment
  3. 2026-07-29 12:38 UTCEG score recompute
  4. 2026-07-29 12:38 UTCGHSA enrichment
  5. 2026-07-29 11:32 UTCEG score recompute
  6. 2026-07-29 10:23 UTCEG score recompute
  7. 2026-07-29 10:22 UTCMITRE cvelistV5first tracked

Related CVEs(same CWE)

Frequently asked(4)

What is CVE-2026-56389?
CVE-2026-56389 is a medium vulnerability published on July 29, 2026. 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…
When was CVE-2026-56389 disclosed?
CVE-2026-56389 was first published in the National Vulnerability Database on July 29, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
What is the CVSS score of CVE-2026-56389?
CVE-2026-56389 has a CVSS v3 base score of 6.8 (NVD). The EG score is currently aggregating — additional source signals are being incorporated as they become available..
How do I remediate CVE-2026-56389?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-56389, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

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