cve/2020/CVE-2020-24240.md

### [CVE-2020-24240](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2020-24240)
![](https://img.shields.io/static/v1?label=Product&message=n%2Fa&color=blue)
![](https://img.shields.io/static/v1?label=Version&message=n%2Fa&color=blue)
![](https://img.shields.io/static/v1?label=Vulnerability&message=n%2Fa&color=brighgreen)

### 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.

### POC

#### Reference
- https://lists.gnu.org/r/bug-bison/2020-07/msg00051.html
- https://lists.gnu.org/r/bug-bison/2020-07/msg00051.html

#### Github
No PoCs found on GitHub currently.