TI-2020-14854 Aliases CVE-2020-24240 GHSA-5xv5-wxfg-845r

GNU Bison before 3.7.1 has a use-after-free in _obstack_free in lib/obstack.c (called…

LOW 27CWE-416Published 2020-08-25 · Updated 2024-08-04

Key facts

Attack vector: Local
Privileges required: None
User interaction: Required
Attack complexity: Low
Impact type: Denial of service
Confidentiality · integrity · availability: None · None · High
Fix status: Will not fix Red Hat: no fix planned

Attack profile from CVSS 3.1 · NVD. Fix status from CNA and Red Hat. Impact type from CWE-416 and the CVSS impact.

Summary

GNU Bison before 3.7.1 has a use-after-free in _obstack_free in lib/obstack.c (called from gram_lex) when a '\0' byte is encountered. NOTE: there is a risk only if Bison is used with untrusted input, and the observed bug happens to cause unsafe behavior with a specific compiler/architecture. The bug report was intended to show that a crash may occur in Bison itself, not that a crash may occur in code that is generated by Bison.

Why it matters now

EPSS 0.01275 70th percentileScored 2026-11-07

Fix Will not fix Red Hat: no fix planned

SSVC decision points

Not available: CISA has not published SSVC decision points for this record.

Affected products

Vendor	Product	Affected versions	Fixed in	Status	Source
—	—	all versions	—	No fix listed	CNA

— Vendor— Affected all versions Fixed in — No fix listed CNA

CPE configurations NVD · 1

CPE	Versions	Role	Vendor
cpe:2.3:a:gnu:bison:3.7:::::::*	3.7	Vulnerable	GNU

cpe:2.3:a:gnu:bison:3.7:*:*:*:*:*:*:* Versions 3.7 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 →

Product	Status	Plan or fix
Red Hat Enterprise Linux 5	Affected	No fix planned: Out of support scope
Red Hat Enterprise Linux 6	Affected	No fix planned: Out of support scope

Not affected: 2 products

Red Hat Enterprise Linux 7
Red Hat Enterprise Linux 8

Timeline

2026-10-02 Threatist record created from CVE-2020-24240
2026-10-03 Alias added: GHSA-5xv5-wxfg-845r

References

Patch 1

https://github.com/akimd/bison/commit/be95a4fe2951374676efc9454ffee8638faaf68d

Advisory 2

TI-2026-40749 Arbitrary Command Execution in GNU Bison CVSS 4.0MEDIUM 6.8
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

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