GitLab has remediated an issue in GitLab CE/EE affecting all versions from 16.11 before 18.7.6, 18.8 before 18.8.6, and 18.9 before 18.9.2 that could have allowed an authenticated user to cause a denial of service condition due to improper input validation on webhook custom header names under certain conditions.
https://hackerone.com/reports/3415683
https://gitlab.com/gitlab-org/gitlab/-/work_items/582096
https://about.gitlab.com/releases/2026/03/11/patch-release-gitlab-18-9-2-released/