{"id":"CVE-2026-6046","aliases":["GHSA-3vmp-whvv-5v9v","GO-2026-6279"],"title":"Mattermost doesn't validate that a username returned during bot registration belongs to a bot account","summary":"Mattermost doesn't validate that a username returned during bot registration belongs to a bot account","severity":"medium","cvss":5.3,"cvssVector":"CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N","vendor":"mattermost","product":"github.com/mattermost/mattermost-server","ecosystem":"go","affected":["github.com/mattermost/mattermost-server >= 11.6.0, < 11.6.1","github.com/mattermost/mattermost-server >= 11.5.0, < 11.5.5","github.com/mattermost/mattermost-server >= 10.11.0, < 10.11.17","github.com/mattermost/mattermost/server/v8 >= 8.0.0-20250731163400-5b955468ea1e, < 8.0.0-20260428151657-c79c3831061a"],"patched":["github.com/mattermost/mattermost-server 11.6.1","github.com/mattermost/mattermost-server 11.5.5","github.com/mattermost/mattermost-server 10.11.17","github.com/mattermost/mattermost/server/v8 8.0.0-20260428151657-c79c3831061a"],"published":"2026-06-12","updated":"2026-09-10","sourceUpdated":"2026-09-10T03:50:55.370444496Z","source":"OSV","sourceUrl":"https://osv.dev/vulnerability/GHSA-3vmp-whvv-5v9v","references":[{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-6046"},{"url":"https://github.com/mattermost/mattermost/pull/36320"},{"url":"https://github.com/mattermost/mattermost/pull/36318"},{"url":"https://github.com/mattermost/mattermost/pull/36317"},{"url":"https://github.com/mattermost/mattermost/pull/36305"},{"url":"https://github.com/mattermost/mattermost/pull/36064"},{"url":"https://github.com/mattermost/mattermost/commit/f706d1f01e6dfe62cab86c1d257f237daa78106a"},{"url":"https://github.com/mattermost/mattermost/commit/c79c3831061a0880c0962c7d567c9e24dd35f44c"},{"url":"https://github.com/mattermost/mattermost/commit/aba9339a24d4b287edd77377c19901d6e341bb96"},{"url":"https://github.com/mattermost/mattermost/commit/98f9778cec1e7f3d97b3d4692fb91f8e7b659972"},{"url":"https://github.com/mattermost/mattermost/commit/3be10297c14d272f273d747af70728f9d03c60ec"},{"url":"https://github.com/mattermost/mattermost/releases/tag/v10.11.16"},{"url":"https://github.com/mattermost/mattermost/releases/tag/v11.5.5"},{"url":"https://github.com/mattermost/mattermost/releases/tag/v11.6.2"},{"url":"https://github.com/mattermost/mattermost/releases/tag/v11.7.0"},{"url":"https://mattermost.com/security-updates"},{"url":"https://github.com/mattermost/mattermost"}],"tags":["osv","go"],"epss":0.0019,"epssPercentile":0.08924,"ingestedAt":"2026-08-25T19:26:22.826Z","slug":"CVE-2026-6046","body":"## Overview\n\nMattermost versions 11.6.x <= 11.6.1, 11.5.x <= 11.5.4, 10.11.x <= 10.11.15, 10.11.x <= 10.11.16 fail to validate that a username returned during bot registration belongs to a bot account, which allows an unprivileged attacker to intercept private messages sent by plugins via direct message channels by pre-registering a user account with a predictable plugin bot username. Mattermost Advisory ID: MMSA-2026-00649\n\n## Affected packages\n\n- `github.com/mattermost/mattermost-server >= 11.6.0, < 11.6.1`\n- `github.com/mattermost/mattermost-server >= 11.5.0, < 11.5.5`\n- `github.com/mattermost/mattermost-server >= 10.11.0, < 10.11.17`\n- `github.com/mattermost/mattermost/server/v8 >= 8.0.0-20250731163400-5b955468ea1e, < 8.0.0-20260428151657-c79c3831061a`\n\n## Remediation\n\nUpgrade to a patched release:\n\n- `github.com/mattermost/mattermost-server 11.6.1`\n- `github.com/mattermost/mattermost-server 11.5.5`\n- `github.com/mattermost/mattermost-server 10.11.17`\n- `github.com/mattermost/mattermost/server/v8 8.0.0-20260428151657-c79c3831061a`","depth":"sunlit","depthScore":29,"depthScoreParts":{"impact":29.2,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}