{"id":"CVE-2026-18551","revision":"9caa3d32bdb846f79f86929c801a4279","records":[{"revision":"9caa3d32bdb846f79f86929c801a4279","observedAt":"2026-10-23T15:48:27.903+00:00","statement":{"source":"cve-program","id":"CVE-2026-18551","aliases":[],"title":"Mattermost guest account privilege escalation via member roles API","description":"Mattermost versions 11.10.x <= 11.10.0, 11.7.x <= 11.7.9, 11.9.x <= 11.9.1, 11.8.x <= 11.8.5 fail to validate the combination of guest and admin scheme roles which allows an authenticated attacker to escalate a guest account to team or channel admin via a crafted PUT request to the member roles API endpoint.. Mattermost Advisory ID: MMSA-2026-00752","state":0,"publishedAt":"2026-10-16T06:56:51.996+00:00","modifiedAt":"2026-10-20T13:11:28.823+00:00","affected":[{"ecosystem":"Vendor product","name":"Mattermost","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"defaultStatus\": \"unaffected\",\n                    \"product\": \"Mattermost\",\n                    \"vendor\": \"Mattermost\",\n                    \"versions\": [\n                        {\n                            \"lessThanOrEqual\": \"11.10.0\",\n                            \"status\": \"affected\",\n                            \"version\": \"11.10.0\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"lessThanOrEqual\": \"11.7.9\",\n                            \"status\": \"affected\",\n                            \"version\": \"11.7.0\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"lessThanOrEqual\": \"11.9.1\",\n                            \"status\": \"affected\",\n                            \"version\": \"11.9.0\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"lessThanOrEqual\": \"11.8.5\",\n                            \"status\": \"affected\",\n                            \"version\": \"11.8.0\",\n                            \"versionType\": \"semver\"\n                        },\n                        {\n                            \"version\": \"11.11.0\",\n                            \"status\": \"unaffected\"\n                        },\n                        {\n                            \"version\": \"11.10.1\",\n                            \"status\": \"unaffected\"\n                        },\n                        {\n                            \"version\": \"11.7.10\",\n                            \"status\": \"unaffected\"\n                        },\n                        {\n                            \"version\": \"11.9.2\",\n                            \"status\": \"unaffected\"\n                        },\n                        {\n                            \"version\": \"11.8.6\",\n                            \"status\": \"unaffected\"\n                        }\n                    ]\n                }"}],"metrics":[{"system":"CVSS 3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:N","score":6.5,"severity":"MEDIUM"}],"references":["https://mattermost.com/security-updates"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-18551","license":"CVE Program Terms of Use","key":"cve-program:CVE-2026-18551","identifiers":["CVE-2026-18551"]},"retained":false,"historicalAffected":[]}],"coverage":[]}