Cross-site scripting in GitLab Web IDE asset serving via path equivalence flaw
CVE-2026-5816 is a path equivalence and improper path validation vulnerability in the Web IDE asset serving component of GitLab CE/EE. It affects GitLab 18.10.x before 18.10.4 and 18.11.x before 18.11.1. The vulnerable logic failed to correctly normalize and validate URL paths before serving Web IDE assets, allowing path equivalence tricks such as dot-segment traversal or encoded separator variants to bypass path-based checks under certain conditions. A remote, unauthenticated attacker can craft a malicious URL that causes attacker-controlled JavaScript to be served and executed in the browser context of an authenticated GitLab user who visits the link. In practice, this is an unauthenticated XSS condition arising from improper resolution of path equivalence in Web IDE asset handling.
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Recent activity
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An improper path validation vulnerability in GitLab CE/EE that could allow an unauthenticated user to execute arbitrary JavaScript in a user's browser session under certain conditions.
A path equivalence flaw in GitLab Web IDE asset serving that leads to unauthenticated cross-site scripting (XSS) in authenticated users' browser sessions, enabling session hijacking and potentially administrative takeover or unauthorized code commits.
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Every observed campaign linking this CVE to a named adversary.
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Cross-references every affected SKU, including bundled OEM variants.
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