CVE-2026-56390: Arbitrary Output Location Change in GNU Bison
CSIRTS triage
- What
- Bison can be configured or coerced to write output files to arbitrary locations.
- Who is affected
- Build systems and scripts using GNU Bison with untrusted input or configuration files.
- Urgency
- Unknown severity; impact depends on build environment permissions and attacker capabilities.
- Action
- Apply Bison patch restricting output file location or review build system invocations.
AI-assisted analysis generated from the source advisory — verify against the original.
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Details
Original advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-56390
Exploitation outlook
EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.
- Low exploitation riskCVE-2026-563900.13% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 2% of all EPSS-scored CVEs.
Referenced CVEs
| CVE | CSIRTS overview | External |
|---|---|---|
| CVE-2026-56390 | coverage & exploitation status | NVD · CVE.org |
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