CVE-2021-33642 Denial of service in byacc

Medium 5.5 Published 20 Jan 2023 Updated 2 Apr 2025

An attacker can cause a denial of service in byacc by triggering an infinite loop during file processing.

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-2021-33642?

CVE-2021-33642 is a medium-severity denial of service vulnerability in byacc, published on 20 Jan 2023. 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

When a file is processed, an infinite loop occurs in next_inline() of the more_curly() function.

Weakness: CWE-835

Which versions are affected by CVE-2021-33642?

It affects 1 product.

Products include Openeuler Byacc.

How do I fix CVE-2021-33642?

Apply the vendor's patch.

Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.

Is CVE-2021-33642 being exploited?

There is no known exploitation of CVE-2021-33642 in the wild and no public exploit code.

CVE-2021-33641 Use after free in byacc High 7.8

Sources

Also known as GHSA-q8mx-78gm-98mh.