{"id":"GHSA-8r89-8w26-cq32","revision":"569306a60be4447cbaecf838faa74c90","records":[{"revision":"569306a60be4447cbaecf838faa74c90","observedAt":"2026-10-24T13:19:41.952+00:00","statement":{"source":"osv","id":"GHSA-8r89-8w26-cq32","aliases":["CVE-2026-5163","GO-2026-5263"],"title":"Mattermost doesn't verify channel membership when processing AI-assisted message rewrites","description":"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","state":0,"publishedAt":"2026-05-18T09:31:48+00:00","modifiedAt":"2026-06-25T19:56:31.4845345+00:00","affected":[{"ecosystem":"Go","name":"github.com/mattermost/mattermost/server/v8","ranges":[{"type":"SEMVER","events":[{"kind":"introduced","version":"11.5.0"},{"kind":"fixed","version":"11.5.2"}]}],"versions":[],"rawVersionEvidence":null},{"ecosystem":"Go","name":"github.com/mattermost/mattermost/server/v8","ranges":[{"type":"SEMVER","events":[{"kind":"introduced","version":"0"},{"kind":"fixed","version":"8.0.0-20260401090745-f4d1abe7e8f5"}]}],"versions":[],"rawVersionEvidence":null},{"ecosystem":"Go","name":"github.com/mattermost/mattermost-server","ranges":[{"type":"SEMVER","events":[{"kind":"introduced","version":"0"},{"kind":"fixed","version":"5.3.2-0.20260401090745-f4d1abe7e8f5"}]}],"versions":[],"rawVersionEvidence":null}],"metrics":[{"system":"CVSS_V3","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N","score":null,"severity":null},{"system":"Publisher rating","vector":null,"score":null,"severity":"MODERATE"}],"references":["https://nvd.nist.gov/vuln/detail/CVE-2026-5163","https://github.com/mattermost/mattermost/commit/f4d1abe7e8f545f1a87f463fa9fe451c731aebf8","https://github.com/mattermost/mattermost","https://mattermost.com/security-updates"],"sourceUrl":"https://github.com/advisories/GHSA-8r89-8w26-cq32","license":"GitHub Advisory Database · CC-BY-4.0","key":"osv:GHSA-8r89-8w26-cq32","identifiers":["GHSA-8r89-8w26-cq32","CVE-2026-5163","GO-2026-5263"]},"retained":false,"historicalAffected":[]}],"coverage":[]}