CVE-2026-3254
Received Received - Intake
Cross-Site Scripting in GitLab Mermaid Sandbox Allows Content Injection

Publication date: 2026-04-22

Last updated on: 2026-04-23

Assigner: GitLab Inc.

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.
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Meta Information
Published
2026-04-22
Last Modified
2026-04-23
Generated
2026-06-16
AI Q&A
2026-04-22
EPSS Evaluated
2026-06-15
NVD
CVE-2026-3254
EUVD
EUVD-2026-24961
Affected Vendors & Products
Showing 2 associated CPEs
Vendor Product Version / Range
gitlab gitlab 18.11.0
gitlab gitlab 18.11.0
Helpful Resources
Exploitability
CWE
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KEV
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CWE ID Description
CWE-1021 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.
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Executive Summary

This vulnerability in GitLab CE/EE versions from 18.11 before 18.11.1 involves improper input validation in the Mermaid sandbox feature. Under certain conditions, it could allow an authenticated user to load unauthorized content into another user's browser.

Mitigation Strategies

To mitigate this vulnerability, you should upgrade GitLab CE/EE to version 18.11.1 or later, as the issue affecting versions from 18.11 before 18.11.1 has been remediated in that release.

Impact Analysis

The vulnerability could allow an authenticated user to inject unauthorized content into another user's browser, potentially leading to information exposure or manipulation of the user's browsing experience. However, the CVSS score indicates a low severity with no confidentiality or availability impact, but a low impact on integrity.

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