CVE-2026-100691: Hugo versions 0.75.0 through 0.165.x contain a stored cross-site scripting vulnerability: the syntax highlight

Routine

MEDIUM 5.4UPGRADE

CVE-2026-100691 is a medium-severity flaw (CVSS 5.4) affecting hugo. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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 render

Why this priority

No elevated risk signals yet

A fixed release or distro patch exists.

Risk facts

CVSS score	5.4 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	Low
User interaction	Required
EPSS exploit chance	0.2% (top 93%)
CISA exploited list	No
Weakness	CWE-79
Published	2026-09-26
Last modified	2026-09-29

Publisher (CNA): VulnCheck · Vendor: gohugo

Last updated 2026-09-29 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-09-26 14:16 UTCPublished CVE record published
2026-09-29 19:08 UTCUpdated Record last modified

gohugo hugo UPGRADE

Affected: >= 0.75.0 and < 0.166.0

Fixed in: 0.166.0

Safe to downgrade to: a release before 0.75.0

1. Check installed version

apt-cache policy hugo || rpm -q hugo || hugo --version

2. UPGRADE to 0.166.0 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade hugo

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade hugo

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 0.75.0 (Debian / Ubuntu)

apt-cache madison hugo sudo apt install hugo=<VERSION_BEFORE_0.75.0> sudo apt-mark hold hugo

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list hugo sudo dnf downgrade hugo-<VERSION_BEFORE_0.75.0> sudo dnf versionlock add hugo

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-100691?

hugo: upgrade to 0.166.0. Exact commands for each OS are on this page.

Is CVE-2026-100691 being exploited?

CVE-2026-100691 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-100691 affect?

CVE-2026-100691 affects hugo. Severity is medium (CVSS 5.4). 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`

How urgent is CVE-2026-100691?

Priority 21/100. No elevated risk signals yet.

Related CVEs

CVE-2026-44301 HIGH 8.1 UPGRADE Hugo is a static site generator
CVE-2026-50134 MEDIUM 5.8 UPGRADE Hugo is a static site generator
CVE-2026-58403 MEDIUM 6.5 UPGRADE Hugo is a static site generator
CVE-2026-58404 MEDIUM 6.8 UPGRADE Hugo is a static site generator
CVE-2026-50133 MEDIUM 6.1 UPGRADE Hugo is a static site generator

References

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