CVE-2020-24240 Use after free in n/a

Medium 5.5 Published 25 Aug 2020 Updated 4 Aug 2024

A use-after-free vulnerability in GNU Bison allows attackers to cause a denial of service via crafted input containing null bytes.

Exploited in the wild: Not known
Login needed: Not needed
Attackable: Local or same network only
Victim action needed: A user has to click or open something
Fix: Available

What is CVE-2020-24240?

CVE-2020-24240 is a medium-severity use after free vulnerability in n/a, published on 25 Aug 2020. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.

Official 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.

Weakness: CWE-416

Which versions are affected by CVE-2020-24240?

It affects 1 product.

Products include Gnu Bison.

How do I fix CVE-2020-24240?

Upgrade to a fixed version.

Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.

Is CVE-2020-24240 being exploited?

There is no known exploitation of CVE-2020-24240 in the wild and no public exploit code.

Sources

Also known as ALPINE-CVE-2020-24240, CVE-2020-16132, DEBIAN-CVE-2020-24240, GHSA-5xv5-wxfg-845r, OESA-2022-1767, UBUNTU-CVE-2020-24240.