CVE-2020-13343: 
GitLab vulnerability analysis and mitigation

An unauthorized access vulnerability was discovered in GitLab affecting all versions starting from 11.2, where unauthorized users could view custom project templates. The vulnerability was assigned CVE-2020-13343 and was publicly disclosed on October 1, 2020 (GitLab Release).

The vulnerability stems from a security flaw in the ProjectsFinder functionality where it uses an initial collection of projects that the authenticated user can access but fails to properly validate the user's access level. This oversight allows access to projects that are public but have restricted access settings for Repository, Issues, and Snippets for Guest users (GitLab Issue). The vulnerability has received a CVSS v3.1 base score of 8.8 (HIGH) from NVD with the vector string CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H (NVD).

The vulnerability allows unauthorized users to view private custom project templates, potentially exposing sensitive project information that should be restricted. This affects both GitLab Community Edition (CE) and Enterprise Edition (EE) installations (GitLab Release).

The vulnerability can be exploited by accessing the available_custom_project_templates method on the User model, which incorrectly returns projects regardless of the user's actual permission level (GitLab Issue).

GitLab has addressed this vulnerability in versions 13.4.2, 13.3.7, and 13.2.10. It is strongly recommended that all installations running affected versions be upgraded to the latest version immediately (GitLab Release).