{"id":"CVE-2026-8821","state":"PUBLISHED","title":"Playbooks run owner channel membership permission bypass","description":"Mattermost versions 11.9.x <= 11.9.0, 11.8.x <= 11.8.4, 11.7.x <= 11.7.7, 10.11.x <= 10.11.22 fail to validate channel member-management permission during playbook run creation, allowing an authenticated channel member to add an arbitrary user to a restricted channel via the run owner field.. Mattermost Advisory ID: MMSA-2026-00677","publishedAt":"2026-09-14T10:42:42.672Z","updatedAt":"2026-09-14T11:19:44.842Z","severity":{"score":7.1,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:N","source":"Mattermost"},"assigner":"Mattermost","products":["Mattermost Mattermost"],"affected":[{"vendor":"Mattermost","product":"Mattermost","defaultStatus":"unaffected","versions":[{"version":"11.9.0","status":"affected","lessThanOrEqual":"11.9.0","versionType":"semver"},{"version":"11.8.0","status":"affected","lessThanOrEqual":"11.8.4","versionType":"semver"},{"version":"11.7.0","status":"affected","lessThanOrEqual":"11.7.7","versionType":"semver"},{"version":"10.11.0","status":"affected","lessThanOrEqual":"10.11.22","versionType":"semver"},{"version":"11.10.0","status":"unaffected"},{"version":"11.9.1","status":"unaffected"},{"version":"11.8.5","status":"unaffected"},{"version":"11.7.8","status":"unaffected"},{"version":"10.11.23","status":"unaffected"}]}],"references":["https://mattermost.com/security-updates"],"weaknesses":["CWE-862"],"ingestedAt":"2026-10-29T20:13:26.108Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/8xxx/CVE-2026-8821.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-8821","state":"PUBLISHED","datePublished":"2026-09-14T10:42:42.672Z","dateUpdated":"2026-09-14T11:19:44.842Z","assignerShortName":"Mattermost","assignerOrgId":"9302f53e-dde5-4bf3-b2f2-a83f91ac0eee","dateReserved":"2026-05-18T09:19:00.475Z"},"containers":{"cna":{"title":"Playbooks run owner channel membership permission bypass","descriptions":[{"lang":"en","value":"Mattermost versions 11.9.x <= 11.9.0, 11.8.x <= 11.8.4, 11.7.x <= 11.7.7, 10.11.x <= 10.11.22 fail to validate channel member-management permission during playbook run creation, allowing an authenticated channel member to add an arbitrary user to a restricted channel via the run owner field.. Mattermost Advisory ID: MMSA-2026-00677"}],"affected":[{"vendor":"Mattermost","product":"Mattermost","defaultStatus":"unaffected","versions":[{"version":"11.9.0","status":"affected","lessThanOrEqual":"11.9.0","versionType":"semver"},{"version":"11.8.0","status":"affected","lessThanOrEqual":"11.8.4","versionType":"semver"},{"version":"11.7.0","status":"affected","lessThanOrEqual":"11.7.7","versionType":"semver"},{"version":"10.11.0","status":"affected","lessThanOrEqual":"10.11.22","versionType":"semver"},{"version":"11.10.0","status":"unaffected"},{"version":"11.9.1","status":"unaffected"},{"version":"11.8.5","status":"unaffected"},{"version":"11.7.8","status":"unaffected"},{"version":"10.11.23","status":"unaffected"}]}],"references":[{"url":"https://mattermost.com/security-updates","name":"MMSA-2026-00677","tags":["vendor-advisory"]}],"metrics":[{"cvssV3_1":{"attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"LOW","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"HIGH","integrityImpact":"LOW","availabilityImpact":"NONE","version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:N","baseSeverity":"HIGH","baseScore":7.1},"format":"CVSS","scenarios":[{"lang":"en","value":"GENERAL"}]}],"problemTypes":[{"descriptions":[{"cweId":"CWE-862","lang":"en","type":"CWE","description":"CWE-862: Missing Authorization"}]}],"providerMetadata":{"shortName":"Mattermost","orgId":"9302f53e-dde5-4bf3-b2f2-a83f91ac0eee","dateUpdated":"2026-09-14T10:42:42.672Z"},"credits":[{"lang":"en","type":"finder","value":"ilent0"}],"solutions":[{"value":"Update Mattermost to versions 11.10.0, 11.9.1, 11.8.5, 11.7.8, 10.11.23 or higher.","lang":"en"}],"source":{"advisory":"MMSA-2026-00677","defect":["https://mattermost.atlassian.net/browse/MM-68695"],"discovery":"EXTERNAL"},"x_generator":{"engine":"cvelib 1.8.0"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"id":"CVE-2026-8821","role":"CISA Coordinator","options":[{"Exploitation":"none"},{"Automatable":"no"},{"Technical Impact":"partial"}],"version":"2.0.3","timestamp":"2026-09-14T11:03:09.855978Z"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-09-14T11:19:44.842Z"}}]}}}