{"id":"CVE-2026-4055","aliases":["GHSA-6cfr-wp44-6qmv","GO-2026-5173"],"url":"https://o3.security/vulnerability/CVE-2026-4055","summary":"Insufficient permission validation on cross-team playbook run creation","details":"Mattermost versions 11.5.x <= 11.5.1 fail to validate team-level run_create permission against the target team when creating a playbook run which allows an authenticated team member to create runs in teams where they lack permission via specifying a different team ID in the run creation API request. Mattermost Advisory ID: MMSA-2026-00629","published":"2026-05-21T07:13:31.669Z","modified":"2026-08-12T03:51:18.821724584Z","cvss":{"score":4.3,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N"},"epss":{"score":0.00152,"percentile":0.04896,"asOf":"2026-08-18"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"Go","name":"github.com/mattermost/mattermost/server/v8","fixedVersion":"8.0.0-20260320113102-f2b3d1c6a945"}],"fix":null,"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/4xxx/CVE-2026-4055.json"},{"type":"ADVISORY","url":"https://mattermost.com/security-updates"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-4055"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T03:51:18.821724584Z"}}