CVE-2026-9859

{"id": "CVE-2026-9859", "cveTags": [], "metrics": {"ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2026-9859", "role": "CISA Coordinator", "options": [{"exploitation": "none"}, {"automatable": "no"}, {"technicalImpact": "partial"}], "version": "2.0.3", "timestamp": "2026-08-18T14:21:26.306030Z"}}], "cvssMetricV31": [{"type": "Secondary", "source": "responsibledisclosure@mattermost.com", "cvssData": {"scope": "UNCHANGED", "version": "3.1", "baseScore": 6.5, "attackVector": "NETWORK", "baseSeverity": "MEDIUM", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N", "integrityImpact": "NONE", "userInteraction": "NONE", "attackComplexity": "LOW", "availabilityImpact": "NONE", "privilegesRequired": "LOW", "confidentialityImpact": "HIGH"}, "impactScore": 3.6, "exploitabilityScore": 2.8}]}, "affected": [{"source": "responsibledisclosure@mattermost.com", "affectedData": [{"vendor": "Mattermost", "product": "Mattermost", "versions": [{"status": "affected", "version": "11.7.0", "versionType": "semver", "lessThanOrEqual": "11.7.6"}, {"status": "affected", "version": "10.11.0", "versionType": "semver", "lessThanOrEqual": "10.11.21"}, {"status": "affected", "version": "11.8.0", "versionType": "semver", "lessThanOrEqual": "11.8.3"}, {"status": "unaffected", "version": "11.9.0"}, {"status": "unaffected", "version": "11.7.7"}, {"status": "unaffected", "version": "10.11.22"}, {"status": "unaffected", "version": "11.8.4"}], "defaultStatus": "unaffected"}]}], "published": "2026-08-17T22:17:27.343", "references": [{"url": "https://mattermost.com/security-updates", "tags": ["Vendor Advisory"], "source": "responsibledisclosure@mattermost.com"}], "vulnStatus": "Analyzed", "weaknesses": [{"type": "Secondary", "source": "responsibledisclosure@mattermost.com", "description": [{"lang": "en", "value": "CWE-863"}]}], "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 enforce PermissionManageBoardRoles on the channelId field of the batch endpoint, which allows an authenticated board editor to relink any board they can edit to an arbitrary channel via a crafted PATCH request. Mattermost Advisory ID: MMSA-2026-00686"}], "lastModified": "2026-08-19T13:28:57.893", "configurations": [{"nodes": [{"negate": false, "cpeMatch": [{"criteria": "cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "B064B1E6-B324-4701-8A07-A0B0028C73BB", "versionEndExcluding": "10.11.22", "versionStartIncluding": "10.11.0"}, {"criteria": "cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "DA4EEA22-A3E7-43AF-91F7-4B597F944100", "versionEndExcluding": "11.7.7", "versionStartIncluding": "11.7.0"}, {"criteria": "cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "DE5EDDAA-76F1-4449-91BB-AFE517AD7B55", "versionEndExcluding": "11.8.4", "versionStartIncluding": "11.8.0"}], "operator": "OR"}]}], "sourceIdentifier": "responsibledisclosure@mattermost.com"}