CVE-2026-16255

Incorrect Authorization in GitLab

GitLab GitLabApplications & CMS

CVSS

5.9Medium

ExploitationNo known exploitationNot in CISA KEV, which does not prove it is unexploitedCISA KEV

Exploit odds (EPSS)0.21%Chance of exploitation activity in the next 30 days, higher than 10% of CVEs. Scored 23 Oct 2026FIRST EPSS

Fixed in19.3.6Also 19.4.3, 19.5.1CVE List

Published21 Oct 2026Updated 21 Oct 2026CVE List

What fixes it

19.3.6GitLabCVE List
19.4.3GitLabCVE List
19.5.1GitLabCVE List

A fixed version on one release line is not the upgrade target for every line. Check your exact version and any vendor backports.

Reports 1

1 outlet mention it. Reports are not confirmation; each links to its source.

GitLab Critical Patch Release: 19.5.1, 19.4.3, 19.3.6, 19.2.9, 19.1.9, 19.0.10, 18.11.13GitLab releases, 21 Oct 2026

Description

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.

Text from CVE List

Affected versions 3

GitLabaffected: 12.0 before 19.3.6CVE List
GitLabaffected: 19.4 before 19.4.3CVE List
GitLabaffected: 19.5 before 19.5.1CVE List