{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-5163", "assignerOrgId": "9302f53e-dde5-4bf3-b2f2-a83f91ac0eee", "state": "PUBLISHED", "assignerShortName": "Mattermost", "dateReserved": "2026-03-30T14:35:03.836Z", "datePublished": "2026-05-18T08:11:13.972Z", "dateUpdated": "2026-05-18T08:11:13.972Z"}, "containers": {"cna": {"affected": [{"defaultStatus": "unaffected", "product": "Mattermost", "vendor": "Mattermost", "versions": [{"lessThanOrEqual": "11.5.1", "status": "affected", "version": "11.5.0", "versionType": "semver"}, {"version": "11.6.0", "status": "unaffected"}, {"version": "11.5.2", "status": "unaffected"}]}], "credits": [{"lang": "en", "type": "finder", "value": "daw10"}], "descriptions": [{"lang": "en", "value": "Mattermost versions 11.5.x <= 11.5.1 fail to verify channel membership when processing AI-assisted message rewrites which allows an authenticated attacker to read the content of threads in private channels and direct messages they do not have access to via a crafted request to the post rewrite endpoint.. Mattermost Advisory ID: MMSA-2026-00645"}], "metrics": [{"cvssV3_1": {"attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "LOW", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "NONE", "availabilityImpact": "NONE", "version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N", "baseSeverity": "MEDIUM", "baseScore": 6.5}, "format": "CVSS", "scenarios": [{"lang": "en", "value": "GENERAL"}]}], "problemTypes": [{"descriptions": [{"lang": "en", "type": "CWE", "description": "CWE-862: Missing Authorization", "cweId": "CWE-862"}]}], "references": [{"url": "https://mattermost.com/security-updates", "name": "MMSA-2026-00645", "tags": ["vendor-advisory"]}], "solutions": [{"value": "Update Mattermost to versions 11.6.0, 11.5.2 or higher.", "lang": "en"}], "source": {"advisory": "MMSA-2026-00645", "defect": ["https://mattermost.atlassian.net/browse/MM-68139"], "discovery": "EXTERNAL"}, "title": "Missing authorization check in AI message rewrite endpoint allows access to private thread content", "providerMetadata": {"orgId": "9302f53e-dde5-4bf3-b2f2-a83f91ac0eee", "shortName": "Mattermost", "dateUpdated": "2026-05-18T08:11:13.972Z"}, "x_generator": {"engine": "cvelib 1.8.0"}}}}

{}

{"cveTags": [], "descriptions": [{"lang": "en", "value": "Mattermost versions 11.5.x <= 11.5.1 fail to verify channel membership when processing AI-assisted message rewrites which allows an authenticated attacker to read the content of threads in private channels and direct messages they do not have access to via a crafted request to the post rewrite endpoint.. Mattermost Advisory ID: MMSA-2026-00645"}], "id": "CVE-2026-5163", "lastModified": "2026-05-18T09:16:23.273", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "NETWORK", "availabilityImpact": "NONE", "baseScore": 6.5, "baseSeverity": "MEDIUM", "confidentialityImpact": "HIGH", "integrityImpact": "NONE", "privilegesRequired": "LOW", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N", "version": "3.1"}, "exploitabilityScore": 2.8, "impactScore": 3.6, "source": "responsibledisclosure@mattermost.com", "type": "Secondary"}]}, "published": "2026-05-18T09:16:23.273", "references": [{"source": "responsibledisclosure@mattermost.com", "url": "https://mattermost.com/security-updates"}], "sourceIdentifier": "responsibledisclosure@mattermost.com", "vulnStatus": "Received", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-862"}], "source": "responsibledisclosure@mattermost.com", "type": "Secondary"}]}

{}

{"affected": [{"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[11.5.0,11.5.1]"}}, {"platform": null, "status": "unaffected", "versions": {"scheme": "semver", "value": "11.6.0"}}, {"platform": null, "status": "unaffected", "versions": {"scheme": "semver", "value": "11.5.2"}}], "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": "2026-05-18T10:30:23.073041+00:00", "updated": "2026-05-18T10:30:23.073078+00:00", "vendors": ["mattermost", "mattermost$PRODUCT$mattermost"]}