{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-9816", "assignerOrgId": "9302f53e-dde5-4bf3-b2f2-a83f91ac0eee", "state": "PUBLISHED", "assignerShortName": "Mattermost", "dateReserved": "2026-05-28T09:54:00.723Z", "datePublished": "2026-08-17T22:05:24.910Z", "dateUpdated": "2026-08-17T22:05:24.910Z"}, "containers": {"cna": {"affected": [{"defaultStatus": "unaffected", "product": "Mattermost", "vendor": "Mattermost", "versions": [{"lessThanOrEqual": "11.7.6", "status": "affected", "version": "11.7.0", "versionType": "semver"}, {"lessThanOrEqual": "10.11.21", "status": "affected", "version": "10.11.0", "versionType": "semver"}, {"lessThanOrEqual": "11.8.3", "status": "affected", "version": "11.8.0", "versionType": "semver"}, {"version": "11.9.0", "status": "unaffected"}, {"version": "11.7.7", "status": "unaffected"}, {"version": "10.11.22", "status": "unaffected"}, {"version": "11.8.4", "status": "unaffected"}]}], "credits": [{"lang": "en", "type": "finder", "value": "kamil-sawicki"}], "descriptions": [{"lang": "en", "value": "Mattermost versions 11.7.x <= 11.7.6, 10.11.x <= 10.11.21, 11.8.x <= 11.8.3 fail to validate BoardMember.Scheme* fields server-side on insert and archive-import paths which allows a board editor or non-guest team member to grant board admin to arbitrary users via POST /api/v2/boards/{boardID}/members and POST /api/v2/teams/{teamID}/archive/import.. Mattermost Advisory ID: MMSA-2026-00685"}], "metrics": [{"cvssV3_1": {"attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "LOW", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "LOW", "integrityImpact": "HIGH", "availabilityImpact": "HIGH", "version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:H/A:H", "baseSeverity": "HIGH", "baseScore": 8.3}, "format": "CVSS", "scenarios": [{"lang": "en", "value": "GENERAL"}]}], "problemTypes": [{"descriptions": [{"lang": "en", "type": "CWE", "description": "CWE-863: Incorrect Authorization", "cweId": "CWE-863"}]}], "references": [{"url": "https://mattermost.com/security-updates", "name": "MMSA-2026-00685", "tags": ["vendor-advisory"]}], "solutions": [{"value": "Update Mattermost to versions 11.9.0, 11.7.7, 10.11.22, 11.8.4 or higher.", "lang": "en"}], "source": {"advisory": "MMSA-2026-00685", "defect": ["https://mattermost.atlassian.net/browse/MM-69022"], "discovery": "EXTERNAL"}, "title": "Insufficient server-side validation of board member role fields permits privilege escalation", "providerMetadata": {"orgId": "9302f53e-dde5-4bf3-b2f2-a83f91ac0eee", "shortName": "Mattermost", "dateUpdated": "2026-08-17T22:05:24.910Z"}, "x_generator": {"engine": "cvelib 1.8.0"}}}}

{}

{"affected": [{"affectedData": [{"defaultStatus": "unaffected", "product": "Mattermost", "vendor": "Mattermost", "versions": [{"lessThanOrEqual": "11.7.6", "status": "affected", "version": "11.7.0", "versionType": "semver"}, {"lessThanOrEqual": "10.11.21", "status": "affected", "version": "10.11.0", "versionType": "semver"}, {"lessThanOrEqual": "11.8.3", "status": "affected", "version": "11.8.0", "versionType": "semver"}, {"status": "unaffected", "version": "11.9.0"}, {"status": "unaffected", "version": "11.7.7"}, {"status": "unaffected", "version": "10.11.22"}, {"status": "unaffected", "version": "11.8.4"}]}], "source": "responsibledisclosure@mattermost.com"}], "cveTags": [], "descriptions": [{"lang": "en", "value": "Mattermost versions 11.7.x <= 11.7.6, 10.11.x <= 10.11.21, 11.8.x <= 11.8.3 fail to validate BoardMember.Scheme* fields server-side on insert and archive-import paths which allows a board editor or non-guest team member to grant board admin to arbitrary users via POST /api/v2/boards/{boardID}/members and POST /api/v2/teams/{teamID}/archive/import.. Mattermost Advisory ID: MMSA-2026-00685"}], "id": "CVE-2026-9816", "lastModified": "2026-08-17T22:17:27.217", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "NETWORK", "availabilityImpact": "HIGH", "baseScore": 8.3, "baseSeverity": "HIGH", "confidentialityImpact": "LOW", "integrityImpact": "HIGH", "privilegesRequired": "LOW", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:H/A:H", "version": "3.1"}, "exploitabilityScore": 2.8, "impactScore": 5.5, "source": "responsibledisclosure@mattermost.com", "type": "Secondary"}]}, "published": "2026-08-17T22:17:27.217", "references": [{"source": "responsibledisclosure@mattermost.com", "url": "https://mattermost.com/security-updates"}], "sourceIdentifier": "responsibledisclosure@mattermost.com", "vulnStatus": "Received", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-863"}], "source": "responsibledisclosure@mattermost.com", "type": "Secondary"}]}

{}

{"affected": [{"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[11.7.0,11.7.6]"}}, {"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[10.11.0,10.11.21]"}}, {"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[11.8.0,11.8.3]"}}, {"platform": null, "status": "unaffected", "versions": {"scheme": "semver", "value": "11.9.0"}}, {"platform": null, "status": "unaffected", "versions": {"scheme": "semver", "value": "11.7.7"}}, {"platform": null, "status": "unaffected", "versions": {"scheme": "semver", "value": "10.11.22"}}, {"platform": null, "status": "unaffected", "versions": {"scheme": "semver", "value": "11.8.4"}}], "enrichment": {"confidence": 100.0, "confidence_source": "matching", "scores": [{"score": 100.0, "source": "matching"}]}, "original": {"product": "Mattermost", "source": "cna", "vendor": "Mattermost"}, "product": "mattermost", "vendor": "mattermost"}], "created": "2026-08-18T00:00:04.890426+00:00", "updated": "2026-08-18T00:15:03.983265+00:00", "vendors": ["mattermost", "mattermost$PRODUCT$mattermost"]}