CVE-2026-3254 Improper Restriction of Rendered UI Layers or Frames in GitLab

Low 3.5 Published 22 Apr 2026 Updated 22 Apr 2026

Authenticated users can load unauthorized content into other users' browsers via improper input validation in the Mermaid sandbox.

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

What is CVE-2026-3254?

CVE-2026-3254 is a low-severity cross-site scripting vulnerability in Gitlab Gitlab, published on 22 Apr 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

GitLab has remediated an issue in GitLab CE/EE affecting all versions from 18.11 before 18.11.1 that under certain conditions could have allowed an authenticated user to load unauthorized content into another user's browser due to improper input validation in the Mermaid sandbox.

Weakness: CWE-1021

Which versions are affected by CVE-2026-3254?

1 open source package ship an affected version, including gitlab. It affects 1 product.

Package	Affected	Fixed in
`gitlab` Bitnami	From `18.11.0`	`18.11.1`

Products include Gitlab Gitlab.

How do I fix CVE-2026-3254?

Upgrade gitlab to 18.11.1 or later.

Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.

Is CVE-2026-3254 being exploited?

There is no known exploitation of CVE-2026-3254 in the wild and no public exploit code.

All Gitlab Gitlab vulnerabilities

Sources

Also known as BIT-gitlab-2026-3254, GHSA-rv75-mvrq-37g2.