Mattermost doesn't validate that a username returned during bot registration belongs to a bot account
Mattermost 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
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describes (1)
Related CVEs.
| ID | severity | exploitable | ||
|---|---|---|---|---|
| CVE-2026-6046US | — | — | ||
Mattermost 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… | ||||
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references
External citations — patches, advisories, analysis.
- https://github.com/mattermost/mattermostPACKAGE
- https://github.com/mattermost/mattermost/commit/3be10297c14d272f273d747af70728f9d03c60ecWEB
- https://github.com/mattermost/mattermost/commit/98f9778cec1e7f3d97b3d4692fb91f8e7b659972WEB
- https://github.com/mattermost/mattermost/commit/aba9339a24d4b287edd77377c19901d6e341bb96WEB
- https://github.com/mattermost/mattermost/commit/c79c3831061a0880c0962c7d567c9e24dd35f44cWEB
- https://github.com/mattermost/mattermost/commit/f706d1f01e6dfe62cab86c1d257f237daa78106aWEB
- https://github.com/mattermost/mattermost/pull/36064WEB
- https://github.com/mattermost/mattermost/pull/36305WEB
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