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Security Advisories: GSA_kwCzR0hTQS01amZ3LWdxNjQtcTQ1Zs4ABBj9

HTML Cleaner allows crafted scripts in special contexts like svg or math to pass through

Impact

The HTML Parser in lxml does not properly handle context-switching for special HTML tags such as <svg>, <math> and <noscript>. This behavior deviates from how web browsers parse and interpret such tags. Specifically, content in CSS comments is ignored by lxml_html_clean but may be interpreted differently by web browsers, enabling malicious scripts to bypass the cleaning process. This vulnerability could lead to Cross-Site Scripting (XSS) attacks, compromising the security of users relying on lxml_html_clean in default configuration for sanitizing untrusted HTML content.

Patches

Users employing the HTML cleaner in a security-sensitive context should upgrade to lxml 0.4.0, which addresses this issue.

Workarounds

As a temporary mitigation, users can configure lxml_html_clean with the following settings to prevent the exploitation of this vulnerability:

remove_tags: Specify tags to remove - their content is moved to their parents' tags.
kill_tags: Specify tags to be removed completely.
allow_tags: Restrict the set of permissible tags, excluding context-switching tags like <svg>, <math> and <noscript>.

References

Permalink: https://github.com/advisories/GHSA-5jfw-gq64-q45f
JSON: https://advisories.ecosyste.ms/api/v1/advisories/GSA_kwCzR0hTQS01amZ3LWdxNjQtcTQ1Zs4ABBj9
Source: GitHub Advisory Database
Origin: Unspecified
Severity: High
Classification: General
Published: about 1 month ago
Updated: about 1 month ago

CVSS Score: 7.7
CVSS vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:L/A:H

EPSS Percentage: 0.00063
EPSS Percentile: 0.28792

Identifiers: GHSA-5jfw-gq64-q45f, CVE-2024-52595
References:

Repository: https://github.com/fedora-python/lxml_html_clean
Blast Radius: 1.0

Affected Packages

pypi:lxml-html-clean

Dependent packages: 26
Dependent repositories: 0
Downloads: 3,145,877 last month
Affected Version Ranges: < 0.4.0
Fixed in: 0.4.0
All affected versions: 0.1.0, 0.1.1, 0.2.0, 0.2.1, 0.2.2, 0.3.0, 0.3.1
All unaffected versions: 0.4.0, 0.4.1