SAML and LDAP Membership Vulnerability in GitLab by GitLab Inc.
CVE-2026-16255

5.9MEDIUM

Key Information:

Vendor

Gitlab
Status
Gitlab
Vendor
CVE Published:
21 October 2026

What is CVE-2026-16255?

GitLab has addressed an access control issue in specific versions of its GitLab EE product, where an instance-wide SAML or LDAP membership lock was not fully enforced. This allowed authenticated users to grant or accept project and group memberships outside of the identity provider's established control, effectively bypassing the security measures intended to manage user permissions. Users running affected versions should update to the patched versions to mitigate the risk of unauthorized access and ensure proper enforcement of membership locks.

Affected Version(s)

GitLab 12.0 < 19.3.6

GitLab 19.4 < 19.4.3

GitLab 19.5 < 19.5.1

References

https://gitlab.com/gitlab-org/gitlab/-/work_items/606479
https://hackerone.com/reports/3809350
technical-descriptionexploitpermissions-required
https://docs.gitlab.com/releases/patches/patch-release-gi...

CVSS V3.1

Score:
5.9
Severity:
MEDIUM
Confidentiality:
High
Integrity:
Low
Availability:
High
Attack Vector:
Network
Attack Complexity:
High
Privileges Required:
Low
User Interaction:
None
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

Credit

Thanks [3nvz](https://hackerone.com/3nvz) for reporting this vulnerability through our HackerOne bug bounty program
.