{"id":"CVE-2026-5139","aliases":["EUVD-2026-38246","GHSA-2g8v-grq3-hq2g","GO-2026-6480"],"status":"published","title":"GitLab Plugin Allows Non-Admin Users to Modify Default Instance Configuration","description":"Mattermost versions 11.7.x \u003c= 11.7.0, 11.6.x \u003c= 11.6.2, 11.5.x \u003c= 11.5.5, 10.11.x \u003c= 10.11.17 fail to enforce administrator authorization on the {{setDefaultInstance}} call within the {{/gitlab connect}} command handler, which allows any authenticated user to overwrite the global default GitLab instance configuration via the {{/gitlab connect \u003cinstance-name\u003e}} slash command.. Mattermost Advisory ID: MMSA-2026-00644","severity":{"version":"3.1","score":5.4,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L","level":"medium","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-11","score":0.00287,"percentile":0.215,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-862"],"published":"2026-06-22T13:34:21Z","modified":"2026-11-07T02:48:28Z","fixes":[{"ecosystem":"Go","package":"github.com/mattermost/mattermost-server","fixed_in":["11.7.1","11.6.3","11.5.6","10.11.18","10.11.18+incompatible","11.5.6+incompatible","11.6.3+incompatible","11.7.1+incompatible"],"sources":["ghsa","osv"]}],"affected":[{"source":"ghsa","ecosystem":"Go","package":"github.com/mattermost/mattermost-server","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"11.7.0"},{"fixed":"11.7.1"}]}]},{"source":"ghsa","ecosystem":"Go","package":"github.com/mattermost/mattermost-server","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"11.6.0"},{"fixed":"11.6.3"}]}]},{"source":"ghsa","ecosystem":"Go","package":"github.com/mattermost/mattermost-server","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"11.5.0"},{"fixed":"11.5.6"}]}]},{"source":"ghsa","ecosystem":"Go","package":"github.com/mattermost/mattermost-server","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"10.11.0"},{"fixed":"10.11.18"}]}]},{"source":"osv","ecosystem":"Go","package":"github.com/mattermost/mattermost-server","ranges":[{"type":"SEMVER","events":[{"introduced":"11.7.0"},{"fixed":"11.7.1"}]}]},{"source":"osv","ecosystem":"Go","package":"github.com/mattermost/mattermost-server","ranges":[{"type":"SEMVER","events":[{"introduced":"11.6.0"},{"fixed":"11.6.3"}]}]},{"source":"osv","ecosystem":"Go","package":"github.com/mattermost/mattermost-server","ranges":[{"type":"SEMVER","events":[{"introduced":"11.5.0"},{"fixed":"11.5.6"}]}]},{"source":"osv","ecosystem":"Go","package":"github.com/mattermost/mattermost-server","ranges":[{"type":"SEMVER","events":[{"introduced":"10.11.0"},{"fixed":"10.11.18"}]}]},{"source":"osv","ecosystem":"Go","package":"github.com/mattermost/mattermost-server","ranges":[{"type":"SEMVER","events":[{"introduced":"10.11.0+incompatible"},{"fixed":"10.11.18+incompatible"},{"introduced":"11.5.0+incompatible"},{"fixed":"11.5.6+incompatible"},{"introduced":"11.6.0+incompatible"},{"fixed":"11.6.3+incompatible"},{"introduced":"11.7.0+incompatible"},{"fixed":"11.7.1+incompatible"}]}]}],"products":[{"vendor":"mattermost","product":"mattermost"},{"vendor":"mattermost","product":"mattermost_server"}],"references":[{"url":"https://mattermost.com/security-updates","tags":["vendor-advisory","Vendor Advisory","advisory","web"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-5139","tags":["advisory"]},{"url":"https://github.com/advisories/GHSA-2g8v-grq3-hq2g","tags":["advisory"]},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/5xxx/CVE-2026-5139.json","tags":["advisory"]},{"url":"https://github.com/mattermost/mattermost","tags":["package"]}],"sources":{"cve":[{"id":"CVE-2026-5139","title":"GitLab Plugin Allows Non-Admin Users to Modify Default Instance Configuration","description":"Mattermost versions 11.7.x \u003c= 11.7.0, 11.6.x \u003c= 11.6.2, 11.5.x \u003c= 11.5.5, 10.11.x \u003c= 10.11.17 fail to enforce administrator authorization on the {{setDefaultInstance}} call within the {{/gitlab connect}} command handler, which allows any authenticated user to overwrite the global default GitLab instance configuration via the {{/gitlab connect \u003cinstance-name\u003e}} slash command.. Mattermost Advisory ID: MMSA-2026-00644","status":"published","published":"2026-06-22T13:34:21.247Z","modified":"2026-06-22T15:39:29.821Z","cvss":[{"version":"3.1","score":5.4,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L","level":"medium","assessor":"cna"}],"cwes":["CWE-862"],"updated_at":"2026-11-02T13:39:27.849196Z"}],"euvd":[{"id":"EUVD-2026-38246","description":"Mattermost versions 11.7.x \u003c= 11.7.0, 11.6.x \u003c= 11.6.2, 11.5.x \u003c= 11.5.5, 10.11.x \u003c= 10.11.17 fail to enforce administrator authorization on the {{setDefaultInstance}} call within the {{/gitlab connect}} command handler, which allows any authenticated user to overwrite the global default GitLab instance configuration via the {{/gitlab connect \u003cinstance-name\u003e}} slash command.. Mattermost Advisory ID: MMSA-2026-00644","status":"published","published":"2026-06-22T13:34:21Z","modified":"2026-06-22T15:39:29Z","cvss":[{"version":"3.1","score":5.4,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L","level":"medium"}],"updated_at":"2026-11-02T18:20:34.745289Z"}],"ghsa":[{"id":"GHSA-2g8v-grq3-hq2g","title":"Mattermost doesn't enforce administrator authorization on the {{setDefaultInstance}} call within the {{/gitlab connect}} command handler","description":"Mattermost versions 11.7.x \u003c= 11.7.0, 11.6.x \u003c= 11.6.2, 11.5.x \u003c= 11.5.5, 10.11.x \u003c= 10.11.17 fail to enforce administrator authorization on the {{setDefaultInstance}} call within the {{/gitlab connect}} command handler, which allows any authenticated user to overwrite the global default GitLab instance configuration via the {{/gitlab connect \u003cinstance-name\u003e}} slash command.. Mattermost Advisory ID: MMSA-2026-00644","status":"published","published":"2026-06-22T15:30:45Z","modified":"2026-09-15T19:51:09Z","cvss":[{"version":"3.1","score":5.4,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L","level":"medium"}],"cwes":["CWE-862"],"updated_at":"2026-11-02T14:41:17.136201Z"}],"nvd":[{"id":"CVE-2026-5139","description":"Mattermost versions 11.7.x \u003c= 11.7.0, 11.6.x \u003c= 11.6.2, 11.5.x \u003c= 11.5.5, 10.11.x \u003c= 10.11.17 fail to enforce administrator authorization on the {{setDefaultInstance}} call within the {{/gitlab connect}} command handler, which allows any authenticated user to overwrite the global default GitLab instance configuration via the {{/gitlab connect \u003cinstance-name\u003e}} slash command.. Mattermost Advisory ID: MMSA-2026-00644","status":"published","published":"2026-06-22T14:17:50.887Z","modified":"2026-06-23T20:50:51.55Z","cvss":[{"version":"3.1","score":5.4,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L","level":"medium","assessor":"secondary"}],"cwes":["CWE-862"],"updated_at":"2026-11-02T14:12:24.912854Z"}],"osv":[{"id":"CVE-2026-5139","title":"GitLab Plugin Allows Non-Admin Users to Modify Default Instance Configuration","description":"Mattermost versions 11.7.x \u003c= 11.7.0, 11.6.x \u003c= 11.6.2, 11.5.x \u003c= 11.5.5, 10.11.x \u003c= 10.11.17 fail to enforce administrator authorization on the {{setDefaultInstance}} call within the {{/gitlab connect}} command handler, which allows any authenticated user to overwrite the global default GitLab instance configuration via the {{/gitlab connect \u003cinstance-name\u003e}} slash command.. Mattermost Advisory ID: MMSA-2026-00644","status":"published","published":"2026-06-22T13:34:21.247Z","modified":"2026-11-07T02:48:28.240470656Z","cvss":[{"version":"3.1","score":5.4,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L","level":"medium"}],"cwes":["CWE-862"],"updated_at":"2026-11-07T03:08:06.729372Z"},{"id":"GHSA-2g8v-grq3-hq2g","title":"Mattermost doesn't enforce administrator authorization on the {{setDefaultInstance}} call within the {{/gitlab connect}} command handler","description":"Mattermost versions 11.7.x \u003c= 11.7.0, 11.6.x \u003c= 11.6.2, 11.5.x \u003c= 11.5.5, 10.11.x \u003c= 10.11.17 fail to enforce administrator authorization on the {{setDefaultInstance}} call within the {{/gitlab connect}} command handler, which allows any authenticated user to overwrite the global default GitLab instance configuration via the {{/gitlab connect \u003cinstance-name\u003e}} slash command.. Mattermost Advisory ID: MMSA-2026-00644","status":"published","published":"2026-06-22T15:30:45Z","modified":"2026-09-28T17:10:54.433442458Z","cvss":[{"version":"3.1","score":5.4,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:L","level":"medium"}],"cwes":["CWE-862"],"updated_at":"2026-11-02T15:46:34.338541Z"},{"id":"GO-2026-6480","title":"Mattermost doesn't enforce administrator authorization on the {{setDefaultInstance}} call within the {{/gitlab connect}} command handler in github.com/mattermost/mattermost-server","description":"Mattermost doesn't enforce administrator authorization on the {{setDefaultInstance}} call within the {{/gitlab connect}} command handler in github.com/mattermost/mattermost-server","status":"published","published":"2026-09-28T16:43:40Z","modified":"2026-09-28T17:00:16.149696592Z","updated_at":"2026-11-02T15:47:03.11707Z"}]}}