KaTeX up to 0.18.1 Renderer trust cross site scripting

Summaryinfo

A vulnerability marked as problematic has been reported in KaTeX up to 0.18.1. The affected element is an unknown function of the component Renderer. This manipulation of the argument trust causes cross site scripting. The identification of this vulnerability is CVE-2026-103923. It is possible to initiate the attack remotely. There is no exploit available. It is suggested to upgrade the affected component.

Detailsinfo

A vulnerability classified as problematic was found in KaTeX up to 0.18.1. Affected by this vulnerability is an unknown code of the component Renderer. The manipulation of the argument trust with an unknown input leads to a cross site scripting vulnerability. The CWE definition for the vulnerability is CWE-79. The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users. As an impact it is known to affect integrity. The summary by CVE is:

KaTeX is a fast, easy-to-use JavaScript library for TeX math rendering on the web. From 0.11.0 until 0.18.2, KaTeX uses ordinary JavaScript property access for the renderer options object, the trust setting, default and processor setting metadata, and namespace lookup and group restoration, allowing inherited properties to be treated as explicitly supplied values. When Object.prototype is already polluted or an attacker controls the options object's prototype, attacker-controlled mathematical expressions can use an inherited trust value to enable trusted rendering and produce links capable of user-interaction cross-site scripting or loading attacker-selected external resources in a consuming application that inserts unsanitized KaTeX output into a page. KaTeX does not itself create the prototype pollution, and rendering an expression alone does not execute script. This issue is fixed in version 0.18.2.

It is possible to read the advisory at github.com. This vulnerability is known as CVE-2026-103923 since 10/01/2026. The exploitation appears to be easy. The attack can be launched remotely. The exploitation doesn't need any form of authentication. It demands that the victim is doing some kind of user interaction. Technical details of the vulnerability are known, but there is no available exploit. The attack technique deployed by this issue is T1059.007 according to MITRE ATT&CK.

Upgrading to version 0.18.2 eliminates this vulnerability.

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Productinfo

Name

• KaTeX

Version

• 0.18.0
• 0.18.1

Website

• Product: https://github.com/KaTeX/KaTeX/

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