CVE-2026-6335: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') in GitLab

Severity: medium (CVSS 5.4 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-05-14 · updated 2026-06-17
Weakness: CWE-79

Description

GitLab has remediated an issue in GitLab CE/EE affecting all versions from 18.11 before 18.11.3 that under certain conditions could have allowed an authenticated user to execute arbitrary code in another user's browser session due to improper sanitization.

Affected products

GitLab: from 18.11.0 before 18.11.3 — fixed in 18.11.3

How to fix

Upgrade to a fixed version: GitLab 18.11.3. Check the vendor advisory for mitigations.

References

https://about.gitlab.com/releases/2026/05/13/patch-release-gitlab-18-11-3-released/
https://gitlab.com/gitlab-org/gitlab/-/work_items/596760
https://hackerone.com/reports/3673647

Get alerted when CVE-2026-6335 or the next vulnerability affects your stack