CVE-2021-33391 Use after free in n/a

Critical 9.8 Published 17 Feb 2023 Updated 18 Mar 2025

An attacker can execute arbitrary code via a use-after-free vulnerability in the HTML Tidy library's CleanNode function.

Exploited in the wild: Not known
Login needed: Not needed
Attackable: Over the internet
Victim action needed: Not needed
Fix: Available

What is CVE-2021-33391?

CVE-2021-33391 is a critical use after free vulnerability in n/a, published on 17 Feb 2023. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

An issue in HTACG HTML Tidy v5.7.28 allows attacker to execute arbitrary code via the -g option of the CleanNode() function in gdoc.c.

Weakness: CWE-416

Which versions are affected by CVE-2021-33391?

It affects 1 product.

Products include Htacg Tidy.

How do I fix CVE-2021-33391?

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-2021-33391 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2021-33391 exists.

Sources

Also known as AZL-13687, AZL-35324, DEBIAN-CVE-2021-33391, GHSA-wfrp-xv2m-8j85, OESA-2024-1017, OESA-2024-1073 and 2 more.