CVE-2020-24240: Use After Free

August 25, 2020 (updated September 2, 2020)

GNU Bison 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.

References

lists.gnu.org/r/bug-bison/2020-07/msg00051.html
nvd.nist.gov/vuln/detail/CVE-2020-24240

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