CVE-2026-5816: Improper Resolution of Path Equivalence in GitLab

Severity: high (CVSS 8.1 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-04-22 · updated 2026-06-17
Weakness: CWE-41

Description

GitLab has remediated an issue in GitLab CE/EE affecting all versions from 18.10 before 18.10.4 and 18.11 before 18.11.1 that could have allowed an unauthenticated user to execute arbitrary JavaScript in a user's browser session due to improper path validation under certain conditions.

Affected products

GitLab: from 18.10.0 before 18.10.4; 18.11.0 — fixed in 18.10.4

How to fix

Upgrade to a fixed version: GitLab 18.10.4. Check the vendor advisory for mitigations.

References

https://about.gitlab.com/releases/2026/04/22/patch-release-gitlab-18-11-1-released/
https://gitlab.com/gitlab-org/gitlab/-/work_items/592816
https://hackerone.com/reports/3572231

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