Intel

AIKIDO-2025-10857

kreuzberg is vulnerable to Permissive Regular Expression

Permissive Regular Expression Pre-CVE
Found by Aikido Intel before public disclosure or CVE publication.
Published Dec 1, 2025

25

Low Risk

This Affects:

PYTHONkreuzberg
3.0.0 - 3.21.0
Fixed in 3.22.0
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TL;DR

Affected versions of this package are vulnerable to injection attacks due to overly permissive regular expressions within the flag for stripping <script> and <style> tags. An attacker can exploit this by injecting a malformed tag where the inner, unclosed substring causes the regex to match too much or too little, allowing the malicious JavaScript payload to remain in the output and execute in a victim's browser.

Who does this affect?

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

Background info

kreuzberg is vulnerable to Permissive Regular Expression in versions 3.0.0 - 3.21.0.

How to fix this

Upgrade the kreuzberg library to the patch version.