GitLab Security Update Fixes High-Severity CVE-2026-5173, 11 Other Flaws

**Executive summary:** GitLab released security updates (18.10.3, 18.9.5, 18.8.9) to fix twelve vulnerabilities affecting self-managed CE/EE installations — notably CVE-2026-5173 (websocket access-control bypass, CVSS 8.5) plus multiple DoS and information-disclosure flaws — and strongly urges immediate upgrades; the advisory includes affected versions, contributors, and upgrade guidance, with no active exploitation reported in this bulletin.