GitLab EE Membership Lock Bypass (v <19.3.6/19.4.3/19.5.1)
CVE-2026-16255 Published on October 21, 2026
Incorrect Authorization in GitLab
GitLab has remediated an issue in GitLab EE affecting all versions from 12.0 before 19.3.6, 19.4 before 19.4.3, and 19.5 before 19.5.1 that, when the instance-wide SAML or LDAP membership lock was enabled, an authenticated user could have granted or accepted project and group membership outside the identity provider's control, due to incomplete enforcement of the membership lock on requests created before the lock was enabled.
Vulnerability Analysis
CVE-2026-16255 can be exploited with network access, and requires small amount of user privileges. This vulnerability is consided to have a high level of attack complexity. The potential impact of an exploit of this vulnerability is considered to have a high impact on confidentiality, with no impact on integrity, and no impact on availability.
Weakness Type
What is an AuthZ Vulnerability?
The software performs an authorization check when an actor attempts to access a resource or perform an action, but it does not correctly perform the check. This allows attackers to bypass intended access restrictions.
CVE-2026-16255 has been classified to as an AuthZ vulnerability or weakness.
Products Associated with CVE-2026-16255
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Affected Versions
GitLab:- Version 12.0 and below 19.3.6 is affected.
- Version 19.4 and below 19.4.3 is affected.
- Version 19.5 and below 19.5.1 is affected.