medium5.3
CVE-2026-6046
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 registrat…
Impact
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
Affected packages
| Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|
| go | github.com/mattermost/mattermost-server | = 11.6.0 | 11.6.1 |
| go | github.com/mattermost/mattermost/server/v8 | >= 8.0.0-20250731163400-5b955468ea1e, < 8.0.0-20260428151657-c79c3831061a | 8.0.0-20260428151657-c79c3831061a |
Affected products
| Vendor | Product | Affected versions |
|---|---|---|
| Mattermost | Mattermost Server | from 10.11.0 before 10.11.17 from 11.5.0 before 11.5.5 from 11.6.0 before 11.6.2 |
Weakness classification
References
- NVD record
- CVE.org record
- GitHub advisory
- https://github.com/advisories/GHSA-3vmp-whvv-5v9v
- https://nvd.nist.gov/vuln/detail/CVE-2026-6046
- https://mattermost.com/security-updates
- https://github.com/mattermost/mattermost/pull/36064
- https://github.com/mattermost/mattermost/pull/36305
- https://github.com/mattermost/mattermost/pull/36317
- https://github.com/mattermost/mattermost/pull/36318
- https://github.com/mattermost/mattermost/pull/36320
- https://github.com/mattermost/mattermost/commit/3be10297c14d272f273d747af70728f9d03c60ec
- https://github.com/mattermost/mattermost/commit/98f9778cec1e7f3d97b3d4692fb91f8e7b659972
- https://github.com/mattermost/mattermost/commit/aba9339a24d4b287edd77377c19901d6e341bb96
- https://github.com/mattermost/mattermost/commit/c79c3831061a0880c0962c7d567c9e24dd35f44c
- https://github.com/mattermost/mattermost/commit/f706d1f01e6dfe62cab86c1d257f237daa78106a
- https://github.com/mattermost/mattermost/releases/tag/v10.11.16
- https://github.com/mattermost/mattermost/releases/tag/v11.5.5
- https://github.com/mattermost/mattermost/releases/tag/v11.6.2
- https://github.com/mattermost/mattermost/releases/tag/v11.7.0