GitLab CE/EE 18.11: Auth User Load Unauth Content via Mermaid Sandbox
CVE-2026-3254 Published on April 22, 2026
Improper Restriction of Rendered UI Layers or Frames in GitLab
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.
Vulnerability Analysis
CVE-2026-3254 is exploitable with network access, requires user interaction and a small amount of user privileges. This vulnerability is considered to have a low attack complexity. The potential impact of an exploit of this vulnerability is considered to have no impact on confidentiality, with no impact on integrity, and no impact on availability.
Weakness Type
What is a Clickjacking Vulnerability?
The web application does not restrict or incorrectly restricts frame objects or UI layers that belong to another application or domain, which can lead to user confusion about which interface the user is interacting with. A web application is expected to place restrictions on whether it is allowed to be rendered within frames, iframes, objects, embed or applet elements. Without the restrictions, users can be tricked into interacting with the application when they were not intending to.
CVE-2026-3254 has been classified to as a Clickjacking vulnerability or weakness.
Products Associated with CVE-2026-3254
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Affected Versions
GitLab:- Version 18.11 and below 18.11.1 is affected.