{"id":"CVE-2026-5163","summary":"Missing authorization check in AI message rewrite endpoint allows access to private thread content","details":"Mattermost versions 11.5.x \u003c= 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","aliases":["GHSA-8r89-8w26-cq32","GO-2026-5263"],"modified":"2026-07-08T08:05:22.958056079Z","published":"2026-05-18T08:11:13.972Z","database_specific":{"cwe_ids":["CWE-862"],"cna_assigner":"Mattermost","osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/5xxx/CVE-2026-5163.json","unresolved_ranges":[{"source":"AFFECTED_FIELD","extracted_events":[{"introduced":"11.5.0"},{"last_affected":"11.5.1"}]}]},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/5xxx/CVE-2026-5163.json"},{"type":"ADVISORY","url":"https://mattermost.com/security-updates"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-5163"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/mattermost/mattermost","events":[{"introduced":"9f2616376582893035a7e3cb38b0fab648bba4e8"},{"fixed":"cc4ef6863ee114bc96be4e34478ec2f0db3eac4e"}],"database_specific":{"source":"CPE_RANGE","cpe":"cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*","extracted_events":[{"introduced":"11.5.0"},{"fixed":"11.5.2"}]}}],"versions":["v11.5.0","v11.5.2-rc2","v11.5.2-rc1","v11.5.1"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-5163.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N"}]}