CVE-2020-24240

MediumCVSS 5.5/10Last modified Jun 17, 2026

Description

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.

Metrics

CVSS 3.1 5.5/10CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H

Weakness enumeration

CWE-416

Affected software

Vendor	Product	Versions
n/a	n/a	n/a

References

https://github.com/akimd/bison/commit/be95a4fe2951374676efc9454ffee8638faaf68dPatch, Third Party Advisory
https://github.com/akimd/bison/compare/v3.7...v3.7.1Third Party Advisory
https://lists.gnu.org/r/bug-bison/2020-07/msg00051.htmlMailing List, Vendor Advisory
https://github.com/akimd/bison/commit/be95a4fe2951374676efc9454ffee8638faaf68dPatch, Third Party Advisory
https://github.com/akimd/bison/compare/v3.7...v3.7.1Third Party Advisory
https://lists.gnu.org/r/bug-bison/2020-07/msg00051.htmlMailing List, Vendor Advisory

Timeline

Published: Aug 25, 2020
Last modified: Jun 17, 2026
NVD status: Modified

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