Intel

AIKIDO-2025-10509

markdown2 is vulnerable to Regular Expression Denial of Service (ReDoS)

Regular Expression Denial of Service (ReDoS) Pre-CVE
Found by Aikido Intel before public disclosure or CVE publication.
Published Jul 30, 2025

23

Low Risk

This Affects:

pythonmarkdown2
1.0.0 - 2.5.3
Fixed in 2.5.4
Are you affected? Scan for Free

TL;DR

Affected versions of this package use a regular expression with inefficient complexity in the HTML tokenizer, specifically within the _run_span_gamut function. This inefficiency can be exploited with specially crafted input to trigger excessive CPU usage, resulting in degraded performance or potential denial-of-service (DoS) conditions due to high computational overhead during parsing.

Who does this affect?

You are affected if you are using a version that falls within the vulnerable range.

Background info

markdown2 is vulnerable to Regular Expression Denial of Service (ReDoS) in versions 1.0.0 - 2.5.3.

How to fix this

Upgrade the markdown2 library to the patch version.