CVE-2025-2256: 
GitLab vulnerability analysis and mitigation

A high-severity vulnerability (CVE-2025-2256) was discovered in GitLab CE/EE affecting all versions from 7.12 before 18.1.6, 18.2 before 18.2.6, and 18.3 before 18.3.2. The vulnerability was disclosed on September 10, 2025, and involves a Denial of Service issue in SAML Responses that could impact GitLab Community Edition and Enterprise Edition installations (GitLab Release, NVD).

The vulnerability allows unauthorized users to render GitLab instances unresponsive to legitimate users by sending multiple concurrent large SAML responses. The issue has been assigned a CVSS v3.1 base score of 7.5 (High) with the vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H. The vulnerability is classified under CWE-1284 (Improper Validation of Specified Quantity in Input) (GitLab Release, NVD).

The vulnerability can result in a denial of service condition, making GitLab instances unresponsive to legitimate users. The attack requires no user interaction or special privileges, making it particularly concerning for organizations relying on SAML authentication (GitLab Release).

GitLab has released patches to address this vulnerability in versions 18.1.6, 18.2.6, and 18.3.2. Organizations are strongly recommended to upgrade their GitLab installations to one of these patched versions immediately. GitLab.com is already running the patched version, and GitLab Dedicated customers do not need to take any action (GitLab Release).

The vulnerability was initially reported through GitLab's HackerOne bug bounty program by security researcher yuki_osaki, demonstrating the effectiveness of GitLab's security response program (GitLab Release).