CVE-2026-6046
Plugin bot username conflict allows user account to be used as bot identity in Mattermost Server
CVSS Score
5.3
EPSS Score
0.0%
EPSS Percentile
0th
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
| CWE | CWE-200 |
| Vendor | mattermost |
| Product | mattermost |
| Published | Jun 12, 2026 |
| Last Updated | Jun 12, 2026 |
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CVSS v3 Breakdown
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N Attack Vector
Network
Attack Complexity
High
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
None
Affected Versions
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
Credits
insomnia1102