CVE-2026-6046 Details
Description
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
A vulnerability exists in Mattermost versions 11.6.x through 11.6.1, 11.5.x through 11.5.4, and 10.11.x through 10.11.16. The issue arises because these versions fail to properly validate that usernames returned during bot registration are associated with bot accounts. This flaw enables an unprivileged attacker to intercept private messages sent by plugins through direct message channels. The attacker can pre-register a user account with a predictable plugin bot username, exploiting the lack of validation to access intercepted messages.
Users can upgrade to Mattermost versions 11.7.0, 11.8.0, or 11.7.0 to address this vulnerability.
Metrics
CVSS 4.0 Severity and Vector Strings:
No CVSS 4.0 data is available for this CVE.
CVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
CISA-ADP
Assessed Jun 12, 2026References to Advisories, Solutions, and Tools
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| URL | Source(s) | Tag(s) |
|---|---|---|
| https://mattermost.com/security-updates | [email protected] | Vendor Advisory |
Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-200 | Exposure of Sensitive Information to an Unauthorized Actor | [email protected] |
Affected Products
| Product | Versions |
|---|---|
| mattermost mattermost server | >= 10.11.0, < 10.11.17 >= 11.5.0, < 11.5.5 >= 11.6.0, < 11.6.2 |
CPE
Remediation
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Change History
4 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Jun 18, 2026 | Initial Analysis | [email protected] |
| Jun 17, 2026 | CVE Modified | [email protected] |
| Jun 17, 2026 | CVE Modified | CISA-ADP |
| Jun 12, 2026 | New CVE Received | [email protected] |