GNU Bison before 3.7.1 has a use-after-free in _obstack_free in lib/obstack.c (called from gram_lex) when a ” 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.
Source: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2020-24240
Reference (s):
- https://github.com/akimd/bison/commit/be95a4fe2951374676efc9454ffee8638faaf68d
- https://github.com/akimd/bison/compare/v3.7 v3.7.1
- https://lists.gnu.org/r/bug-bison/2020-07/msg00051.html