KaTeX: Existing prototype pollution can bypass trust restrictions

CISA KEV is observed exploitation evidence. FIRST EPSS is a dated prediction of exploitation in the next 30 days. Missing scores are unknown. This collector requests predictions only for explicit CVE aliases in the public NuGet archive; Microsoft release views retain their existing prediction scope.

No collected risk observation for these identifiers. This does not establish absence of exploitation or a zero probability.

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.

Source published

1 Oct 2026 17:37:47 UTC

Source modified

6 Oct 2026 01:59:30 UTC

Observed here

23 Oct 2026 15:48:27 UTC

Source terms

CVE Program Terms of Use

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: cve-program · CVE Program Terms of Use. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 4.0 · 2.1 CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N

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.

Source published

Oct 1, 2026, 5:37:47 PM (timezone not stated)

Source modified

Oct 6, 2026, 1:59:30 AM (timezone not stated)

Observed here

11 Nov 2026 05:29:57 UTC

Source terms

ENISA EUVD · source terms and attribution apply

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: euvd · ENISA EUVD · source terms and attribution apply. Source text is retained; field grouping and change labels are provided by ChangeIntel.

EUVD CVSS 4.0 · 2.1 CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N

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.

Source published

1 Oct 2026 18:17:13 UTC

Source modified

6 Oct 2026 02:17:02 UTC

Observed here

25 Oct 2026 04:17:29 UTC

Source terms

NIST NVD usage terms; underlying source attribution retained

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: nvd · NIST NVD usage terms; underlying source attribution retained. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 4.0 · [email protected] · Secondary · 2.1 CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

### Impact KaTeX can act as a read-side prototype pollution gadget in applications where `Object.prototype` has already been polluted, or where an attacker can influence the prototype of the renderer options object. (KaTeX does not enable said prototype pollution. This advisory applies when combining KaTeX with other vulnerable software that allows for prototype pollution.) Affected versions may treat inherited properties from `Object.prototype` as renderer options, internal setting metadata, or namespace entries. In particular, an inherited `trust` value will be treated as though the application explicitly enabled trusted rendering, rather than using the documented default of `false`. With attacker-controlled mathematical expressions, this can produce links capable of user-interaction cross-site scripting or load attacker-selected external resources. Exploitation requires the consuming application to insert KaTeX output into a web page without a separate sanitizer. (KaTeX does not execute scripts merely by rendering an expression.) Other inherited settings can alter rendering behavior or resource limits. Inherited setting metadata can affect how defaults and supplied options are processed, while inherited namespace properties can be mistaken for defined macros or other internal values. ### Patches Upgrade to KaTeX v0.18.2 to remove this vulnerability. ### Workarounds - Address any prototype-pollution vulnerability in the application or its dependencies. - `delete Object.prototype.trust`, `delete Object.prototype.default`, and `delete Object.prototype.processor` before calling KaTeX - Do not allow untrusted input to control the renderer options object or its prototype. - Sanitize KaTeX-generated HTML before inserting it into a document. ### Details KaTeX previously used ordinary JavaScript property access in the following contexts: - Renderer settings could be inherited from the prototype of the options object. - Internal `default` and `processor` setting metadata could be inherited from `Object.prototype`. - Namespace lookup could treat inherited properties as built-in definitions. - Namespace group restoration could preserve an inherited property as though it had been an explicitly defined value. The fix adds own-property checks to each of these paths. Inherited properties are no longer accepted as renderer settings, setting metadata, namespace definitions, or values to be restored after a group ends. ### For more information If you have any questions or comments about this advisory: - Open an issue or security advisory in the [KaTeX repository](https://github.com/KaTeX/KaTeX/) - Email us at [[email protected]](mailto:[email protected])

Source published

5 Oct 2026 23:41:05 UTC

Source modified

6 Oct 2026 00:00:09 UTC

Observed here

24 Oct 2026 13:17:17 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · GitHub Advisory Database · CC-BY-4.0. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS_V4 · CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N

Publisher rating · LOW