Plugin bot username conflict allows user account to be used as bot identity in Mattermost Server
Priority LOW 23CWE-200Published · Updated
Key facts
- Attack vector
- Network
- Privileges required
- Low
- User interaction
- None
- Attack complexity
- High
- Impact type
- Information disclosure
- Confidentiality · integrity · availability
- High · None · None
- Fix status
- Fixed
Attack profile from CVSS 3.1 · CNA. Fix status from CNA and GitHub. Impact type from CWE-200.
Summary
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
Why it matters now
Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.0019 8th percentileScored 2026-11-07
Fix Fixed Mattermost (Mattermost): 11.7.0, 11.6.2, 11.5.5 +2github.com/mattermost/mattermost-server (Go): 11.6.1, 11.5.5, 10.11.17+1 more product
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- No
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| Mattermost | Mattermost | 11.6.0 – 11.6.1; 11.5.0 – 11.5.4; 10.11.0 – 10.11.15; 10.11.0 – 10.11.16 | 11.7.0, 11.6.2, 11.5.5, 10.11.16, 10.11.17 | Patch available | CNA |
| — | github.com/mattermost/mattermost-server (Go) | 11.6.0 to before 11.6.1 | 11.6.1 | Patch available | GHSA-3vmp-whvv-5v9v |
| — | github.com/mattermost/mattermost-server (Go) | 11.5.0 to before 11.5.5 | 11.5.5 | Patch available | GHSA-3vmp-whvv-5v9v |
| — | github.com/mattermost/mattermost-server (Go) | 10.11.0 to before 10.11.17 | 10.11.17 | Patch available | GHSA-3vmp-whvv-5v9v |
| — | github.com/mattermost/mattermost/server/v8 (Go) | 8.0.0-20250731163400-5b955468ea1e to before 8.0.0-20260428151657-c79c3831061a | 8.0.0-20260428151657-c79c3831061a | Patch available | GHSA-3vmp-whvv-5v9v |
- Mattermost VendorMattermost Affected 11.6.0 – 11.6.1; 11.5.0 – 11.5.4; 10.11.0 – 10.11.15; 10.11.0 – 10.11.16 Fixed in 11.7.0, 11.6.2, 11.5.5, 10.11.16, 10.11.17 Patch available CNA
- github.com/mattermost/mattermost-server (Go) Vendor— Affected 11.6.0 to before 11.6.1 Fixed in 11.6.1 Patch available GHSA-3vmp-whvv-5v9v
- github.com/mattermost/mattermost-server (Go) Vendor— Affected 11.5.0 to before 11.5.5 Fixed in 11.5.5 Patch available GHSA-3vmp-whvv-5v9v
- github.com/mattermost/mattermost-server (Go) Vendor— Affected 10.11.0 to before 10.11.17 Fixed in 10.11.17 Patch available GHSA-3vmp-whvv-5v9v
- github.com/mattermost/mattermost/server/v8 (Go) Vendor— Affected 8.0.0-20250731163400-5b955468ea1e to before 8.0.0-20260428151657-c79c3831061a Fixed in 8.0.0-20260428151657-c79c3831061a Patch available GHSA-3vmp-whvv-5v9v
CPE configurations NVD · 1
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:* | 10.11.0 to before 10.11.17; 11.5.0 to before 11.5.5; 11.6.0 to before 11.6.2 | Vulnerable | Mattermost |
- cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:* Versions 10.11.0 to before 10.11.17; 11.5.0 to before 11.5.5; 11.6.0 to before 11.6.2 Vulnerable ·Mattermost
Remediation
- Fix · CNA Mattermost (Mattermost) Fixed in 11.7.0, 11.6.2, 11.5.5, 10.11.16, 10.11.17
- Fix · GHSA-3vmp-whvv-5v9v github.com/mattermost/mattermost-server (Go) Fixed in 11.6.1 Advisory →
- Fix · GHSA-3vmp-whvv-5v9v github.com/mattermost/mattermost-server (Go) Fixed in 11.5.5 Advisory →
- Fix · GHSA-3vmp-whvv-5v9v github.com/mattermost/mattermost-server (Go) Fixed in 10.11.17 Advisory →
- Fix · GHSA-3vmp-whvv-5v9v github.com/mattermost/mattermost/server/v8 (Go) Fixed in 8.0.0-20260428151657-c79c3831061a Advisory →
Timeline
- 2026-10-02 Threatist record created from CVE-2026-6046
- 2026-10-03 Alias added: GHSA-3vmp-whvv-5v9v
References
Other 15
- https://github.com/mattermost/mattermost/pull/36320
- https://github.com/mattermost/mattermost/pull/36318
- https://github.com/mattermost/mattermost/pull/36317
- https://github.com/mattermost/mattermost/pull/36305
- https://github.com/mattermost/mattermost/pull/36064
- https://github.com/mattermost/mattermost/commit/f706d1f01e6dfe62cab86c1d257f237daa78106a
- https://github.com/mattermost/mattermost/commit/c79c3831061a0880c0962c7d567c9e24dd35f44c
- https://github.com/mattermost/mattermost/commit/aba9339a24d4b287edd77377c19901d6e341bb96
- https://github.com/mattermost/mattermost/commit/98f9778cec1e7f3d97b3d4692fb91f8e7b659972
- https://github.com/mattermost/mattermost/commit/3be10297c14d272f273d747af70728f9d03c60ec
- 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
- https://github.com/mattermost/mattermost
More Mattermost Server vulnerabilities
- TI-2025-18933 Arbitrary file read in Mattermost Boards via import & export board archive CVSS 3.1CRITICAL 9.9
- TI-2025-04465 Path Traversal Leading to RCE by Any Authenticated Mattermost User CVSS 3.1CRITICAL 9.9
- TI-2017-14068 An issue was discovered in Mattermost Server before 3.6.2. CVSS 3.1CRITICAL 9.8
- TI-2017-14060 An issue was discovered in Mattermost Server before 3.8.2, 3.7.5, and 3.6.7. CVSS 3.1CRITICAL 9.8
- TI-2017-14048 An issue was discovered in Mattermost Server before 4.1.0, 4.0.4, and 3.10.3. CVSS 3.1CRITICAL 9.8
- TI-2025-14360 Arbitrary file read via block duplication in Mattermost Boards CVSS 3.1CRITICAL 9.9
Sources
- CVE-2026-6046 · CVE Program
- CVE-2026-6046 · NVD
- FIRST EPSS
- GHSA-3vmp-whvv-5v9v · GitHub Advisory Database · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences