#VU46310 Use-after-free in GNU Bison - CVE-2020-24240
Published: August 25, 2020 / Updated: September 7, 2020
Vulnerability identifier: #VU46310
Vulnerability risk: Medium
CVSSv4.0: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Green
CVE-ID: CVE-2020-24240
CWE-ID: CWE-416
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerable software:
GNU Bison
GNU Bison
Software vendor:
GNU
GNU
Description
The vulnerability allows a remote non-authenticated attacker to perform a denial of service (DoS) attack.
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.
Remediation
Install update from vendor's website.