CVE-2024-52595

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

• https://github.com/fedora-python/lxml_html_clean/pull/19
• https://github.com/fedora-python/lxml_html_clean/pull/19/commits/c5d816f86eb3707d72a8ecf5f3823e0daa1b3808

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.

Untrusted input is rendered as active markup in a victim's browser, which can run script in their session. Typical impact: session or credential theft, and actions taken as the user.

CVE-2024-52595 has a CVSS score of 7.7 (High). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (0.4.0); upgrading removes the vulnerable code path.

Kodem intelligence

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

1. What is CVE-2024-52595? CVE-2024-52595 is a high-severity cross-site scripting (XSS) vulnerability in lxml-html-clean (pip), affecting versions < 0.4.0. It is fixed in 0.4.0. Untrusted input is rendered as active markup in a victim's browser, which can run script in their session.
2. How severe is CVE-2024-52595? CVE-2024-52595 has a CVSS score of 7.7 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of lxml-html-clean are affected by CVE-2024-52595? lxml-html-clean (pip) versions < 0.4.0 is affected.
4. Is there a fix for CVE-2024-52595? Yes. CVE-2024-52595 is fixed in 0.4.0. Upgrade to this version or later.
5. Is CVE-2024-52595 exploitable, and should I be worried? Whether CVE-2024-52595 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2024-52595 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2024-52595? Upgrade lxml-html-clean to 0.4.0 or later.