{"id":"CVE-2026-16255","kind":"vulnerability","aliases":["CVE-2026-16255"],"related":[],"title":"GitLab EE: stale requests bypass SAML or LDAP membership lock","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.","summary":"When the instance-wide SAML or LDAP membership lock is enabled, requests created before the lock was turned on can still grant or accept project and group membership outside the identity provider's control. An authenticated user can use this to gain access to projects and groups they should not be able to join.","severity":"medium","cvss":5.9,"epss":0.00209,"exploited":false,"exploited_at":null,"products":[],"ecosystems":[],"tags":["gitlab","ldap","package","saml","self-hosted"],"not_affected_if":["default-config","gitlab-ce"],"how_to_check":"- Check the GitLab version with `gitlab-rake gitlab:env:info` or the admin Version page; affected if below `19.3.6`, between `19.4` and `19.4.2`, or between `19.5` and `19.5.0` on EE installs\n- Check whether the instance-wide SAML or LDAP membership lock is enabled in the Admin Area settings","fix":"- Upgrade GitLab EE to `19.3.6`, `19.4.3`, or `19.5.1` (or later on the same line)\n- Until patched, review project and group memberships created or accepted around the time the membership lock was enabled","status":"open","published_at":"2026-10-22T01:16:59+00:00","first_seen_at":"2026-10-23T21:57:30+00:00","triaged_at":"2026-10-25T04:08:01+00:00","updated_at":"2026-10-25T04:08:01+00:00","category":"package","confidence":0.7,"triage":{"at":"2026-10-25T04:08:01Z","model":"claude-haiku-5-5","output":{"fix":"- Upgrade GitLab EE to `19.3.6`, `19.4.3`, or `19.5.1` (or later on the same line)\n- Until patched, review project and group memberships created or accepted around the time the membership lock was enabled","reach":"network","title":"GitLab EE: stale requests bypass SAML or LDAP membership lock","impact":"medium","summary":"When the instance-wide SAML or LDAP membership lock is enabled, requests created before the lock was turned on can still grant or accept project and group membership outside the identity provider's control. An authenticated user can use this to gain access to projects and groups they should not be able to join.","category":"package","nicknames":[],"who_cares":["gitlab","self-hosted","saml","ldap"],"confidence":0.7,"needs_auth":"yes","worst_case":"Authenticated user gains project and group membership beyond identity provider control","analyst_note":"","how_to_check":"- Check the GitLab version with `gitlab-rake gitlab:env:info` or the admin Version page; affected if below `19.3.6`, between `19.4` and `19.4.2`, or between `19.5` and `19.5.0` on EE installs\n- Check whether the instance-wide SAML or LDAP membership lock is enabled in the Admin Area settings","needs_analyst":false,"not_affected_if":["default-config","gitlab-ce"],"who_is_affected":"Self-managed GitLab EE instances from 12.0 up to the fixed versions that have the instance-wide SAML or LDAP membership lock turned on. The issue requires that the lock was enabled after some membership requests already existed. GitLab.com and instances without the lock enabled are less exposed; the sources do not say how GitLab.com is handled.","user_interaction":"no","needs_special_setup":"yes","severity_if_unknown":"medium"},"cost_usd":0.000656,"input_tokens":3422,"output_tokens":628,"severity_before":"medium"},"analyst_status":null,"analyst_note":null,"search":"'-16255':13A,16A '-2026':12A,15A '12.0':91C '19.3.6':93C '19.4':94C '19.4.3':96C '19.5':98C '19.5.1':100C 'abl':76B 'accept':48B,121C 'access':67B 'affect':87C 'authent':60B,115C 'bypass':5A 'control':58B,131C 'could':117C 'creat':37B,142C 'cve':11A,14A 'due':132C 'ee':2A,86C 'enabl':35B,113C,147C 'enforc':135C 'gain':66B 'gitlab':1A,17B,79C,85C 'grant':46B,119C 'group':51B,71B,124C 'host':23B 'ident':55B,128C 'incomplet':134C 'instanc':27B,105C 'instance-wid':26B,104C 'issu':83C 'join':78B 'ldap':8A,18B,31B,109C 'lock':10A,33B,40B,111C,139C,145C 'membership':9A,32B,52B,110C,125C,138C 'outsid':53B,126C 'packag':19B 'project':49B,69B,122C 'provid':56B,129C 'remedi':81C 'request':4A,36B,141C 'saml':6A,20B,29B,107C 'self':22B 'self-host':21B 'stale':3A 'still':45B 'turn':42B 'use':63B 'user':61B,116C 'version':89C 'wide':28B,106C","nicknames":[],"mitigations":[],"who_affected":"Self-managed GitLab EE instances from 12.0 up to the fixed versions that have the instance-wide SAML or LDAP membership lock turned on. The issue requires that the lock was enabled after some membership requests already existed. GitLab.com and instances without the lock enabled are less exposed; the sources do not say how GitLab.com is handled.","tier":"C","verified":{},"analyst_revisit_at":null,"first_public_at":"2026-10-22T01:16:59+00:00","kev":null,"cvss_vector":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:L/A:N","cvss_by":"cve@gitlab.com","poc_count":0,"sources":[{"source":"nvd","external_id":"CVE-2026-16255","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-16255","severity":null,"published_at":"2026-10-22T01:16:59+00:00","modified_at":"2026-10-22T16:18:19+00:00","first_seen_at":"2026-10-23T21:57:30+00:00","fetched_at":"2026-10-23T22:29:02+00:00","note":null},{"source":"epss","external_id":"CVE-2026-16255","url":"https://api.first.org/data/v1/epss?cve=CVE-2026-16255","severity":null,"published_at":null,"modified_at":null,"first_seen_at":"2026-10-24T07:15:52+00:00","fetched_at":"2026-10-24T07:15:52+00:00","note":null}],"documents":[],"notice":"Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai"}