# CVE-2026-100691: Hugo before 0.166.0 Stored XSS via lineAnchors code block option

> Hugo static site generator allows stored XSS via unescaped lineAnchors in code blocks, enabling JavaScript execution in visitor browsers.

- **Severity:** Medium 5.1 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 26 Sep 2026
- **Updated:** 28 Sep 2026
- **Also known as:** DEBIAN-CVE-2026-100691, GHSA-8v94-8989-vc79, GHSA-q4xf-287f-98r8, MINI-6h29-v3fx-96c7, MINI-6v2g-8j4v-cp5c, UBUNTU-CVE-2026-100691

## What is CVE-2026-100691?

CVE-2026-100691 is a medium-severity cross-site scripting vulnerability in gohugoio hugo, published on 26 Sep 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.

### Official 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.

Weakness: CWE-79 (Improper Neutralization of Input During Web Page Generation)

## Which versions are affected by CVE-2026-100691?

It affects 1 product.


Products: Gohugo Hugo.

## How do I fix CVE-2026-100691?

Upgrade to a fixed version.

## Is CVE-2026-100691 being exploited?

There is no known exploitation of CVE-2026-100691 in the wild and no public exploit code.

## Other vulnerabilities in gohugoio hugo

- [CVE-2026-75926](https://insights.sbomify.com/CVE-2026-75926/): Hugo 0.162.0 to 0.164.x - Node Permission Model Bypass via Default TailwindCSS Child-Process Grant (critical 9.3)
- [CVE-2026-100690](https://insights.sbomify.com/CVE-2026-100690/): Hugo v0.161.0 to v0.165.0 Arbitrary File Read via Symlinks (high 8.7)
- [CVE-2026-100692](https://insights.sbomify.com/CVE-2026-100692/): Hugo before v0.166.0 Path Traversal via Symlinked Mount Roots (high 8.7)
- [CVE-2026-100693](https://insights.sbomify.com/CVE-2026-100693/): Hugo v0.162.0 before v0.166.0 IP-literal Deny Rule Bypass (high 8.6)
- [CVE-2020-26284](https://insights.sbomify.com/CVE-2020-26284/): Hugo can execute a binary from the current directory on Windows (high 7.7)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-100691 and fix it if it is affected.

What it is: CVE-2026-100691 is a medium-severity cross-site scripting vulnerability in gohugoio hugo, published on 26 Sep 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2026-100691 in the wild and no public exploit code.

Affected product: gohugoio hugo. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-100691/ (Markdown: https://insights.sbomify.com/CVE-2026-100691/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-100691
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-100691
- OSV: https://osv.dev/vulnerability/CVE-2026-100691

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-100691/
Summaries are generated and may contain mistakes; the official description above is the record.