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CVE-2020-24240

Published: 25 August 2020

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.

Priority

Low

Cvss 3 Severity Score

5.5

Score breakdown

Status

Package Release Status
bison
Launchpad, Ubuntu, Debian
bionic Needed

focal Needed

groovy Ignored
(end of life)
hirsute Ignored
(end of life)
impish Ignored
(end of life)
jammy Needed

kinetic Ignored
(end of life, was needed)
lunar Not vulnerable
(2:3.8.2+dfsg-1build1)
mantic Not vulnerable
(2:3.8.2+dfsg-1build1)
trusty Does not exist

upstream
Released (3.7.1)
xenial Needed

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

Severity score breakdown

Parameter Value
Base score 5.5
Attack vector Local
Attack complexity Low
Privileges required None
User interaction Required
Scope Unchanged
Confidentiality None
Integrity impact None
Availability impact High
Vector CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H