gohugoio Hugo up to 0.165.x Syntax Highlighter lineAnchors cross site scripting

Summaryinfo

A vulnerability, which was classified as problematic, has been found in gohugoio Hugo up to 0.165.x. This issue affects some unknown processing of the component Syntax Highlighter. Performing a manipulation of the argument lineAnchors results in cross site scripting. This vulnerability was named CVE-2026-100691. The attack may be initiated remotely. There is no available exploit. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability classified as problematic has been found in gohugoio Hugo up to 0.165.x. This affects an unknown functionality of the component Syntax Highlighter. The manipulation of the argument lineAnchors with an unknown input leads to a cross site scripting vulnerability. CWE is classifying the issue as 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. This is going to have an impact on integrity. The summary by CVE is:

Hugo versions 0.75.0 through 0.165.x contain a stored cross-site scripting vulnerability: the syntax highlighter does not escape the `lineAnchors` option before passing it to Chroma, which writes the value verbatim into the `id` and `href` attributes of the generated line-number markup. A crafted `lineAnchors` value supplied as a Markdown code fence attribute (or passed to the `highlight` template function) results in unescaped HTML in the rendered page, allowing arbitrary JavaScript to execute in the browsers of visitors to the generated site. This affects sites that build and publish Markdown from untrusted contributors; Hugo's security model otherwise considers content trusted input. Fixed in 0.166.0, where the `lineAnchors` value is HTML-escaped before being passed to Chroma.

The advisory is shared at github.com. This vulnerability is uniquely identified as CVE-2026-100691 since 09/26/2026. The exploitability is told to be easy. It is possible to initiate the attack remotely. It demands that the victim is doing some kind of user interaction. Technical details are known, but no exploit is available. MITRE ATT&CK project uses the attack technique T1059.007 for this issue.

Upgrading to version 0.166.0 eliminates this vulnerability.

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Productinfo

Vendor

• gohugoio

Name

• Hugo

Version

• 0.165

Website

• Product: https://github.com/gohugoio/hugo/

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