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GHSA-5jfw-gq64-q45f
No affected components available
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
- https://github.com/fedora-python/lxml_html_clean/pull/19
- https://github.com/fedora-python/lxml_html_clean/pull/19/commits/c5d816f86eb3707d72a8ecf5f3823e0daa1b3808
The vulnerability can be exploited over the network without needing physical access. It is difficult for an attacker to exploit this vulnerability and may require special conditions. An attacker does not need any special privileges or access rights. No user interaction is needed for the attacker to exploit this vulnerability. The impact is confined to the system where the vulnerability exists. There is a high impact on the confidentiality of the information. There is a low impact on the integrity of the data. There is a high impact on the availability of the system.
Exploitation activity has been observed. Apply available patches or mitigations urgently.
The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.
We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.
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