{"id":"CVE-2026-5163","title":"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…","summary":"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…","severity":"medium","cvss":6.5,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N","cwe":["CWE-862"],"vendor":"mattermost","product":"mattermost_server","affected":["mattermost_server >= 11.5.0, < 11.5.2"],"patched":["mattermost_server 11.5.2"],"published":"2026-05-18","updated":"2026-10-14","sourceUpdated":"2026-10-14T20:10:00.190","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-5163","references":[{"url":"https://mattermost.com/security-updates","label":"responsibledisclosure@mattermost.com"}],"tags":["nvd"],"epss":0.0034,"epssPercentile":0.25816,"ingestedAt":"2026-10-14T20:53:12.299Z","slug":"CVE-2026-5163","body":"## Overview\n\nMattermost 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\n\n## Affected\n\n- `mattermost_server >= 11.5.0, < 11.5.2`\n\n## Remediation\n\nUpgrade past the affected range:\n\n- `mattermost_server 11.5.2`","depth":"sunlit","depthScore":36,"depthScoreParts":{"impact":35.8,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[]}