CVE-2026-100691

Hugo before 0.166.0 Stored XSS via lineAnchors code block option

MEDIUM
5.4
CVSS Score
Published: September 26, 2026 at 01:23 PM UTC
Updated: September 29, 2026 at 07:08 PM UTC
2 products affected across 2 vendorsHugoHugo

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Severity
MEDIUM5.4
Exploit prediction
EPSS 0.2%
SSVC
No known exploit

Description

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

0.75.0 ≤ v < 0.166.0
Affected range stops below 0.166.0, so it looks safe — our inference, not a vendor statement
0.75.0 ≤ v < 0.166.00.75.0
Vendor states this is fixed in 0.166.0 (unaffected)

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

SSVC — Action Prioritization

SSVCNo known exploitNot automatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

5.4MEDIUMVulnCheck
Attack Vector
NETWORK
Complexity
LOW
Privileges
LOW
User Interaction
REQUIRED
Scope
CHANGED
Confidentiality
LOW
Integrity
LOW
Availability
NONE
Vector?

Quick Info

StatusANALYZED
CWE
CWE-79

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