CVE-2026-6046
Published:June 12, 2026
Updated:June 29, 2026
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
https://github.com/mattermost/mattermost.git (GITHUB):
Affected version(s) >=v11.6.0 <v11.6.2Fix Suggestion:
Update to version v11.6.2https://github.com/mattermost/mattermost.git (GITHUB):
Affected version(s) >=v11.5.0 <v11.5.5Fix Suggestion:
Update to version v11.5.5https://github.com/mattermost/mattermost.git (GITHUB):
Affected version(s) >=v10.11.0 <v10.11.16Fix Suggestion:
Update to version v10.11.16github.com/mattermost/mattermost (GO):
Affected version(s) >=v11.6.0 <v11.6.2Fix Suggestion:
Update to version v11.6.2github.com/mattermost/mattermost (GO):
Affected version(s) >=v10.11.0 <v10.11.16Fix Suggestion:
Update to version v10.11.16github.com/mattermost/mattermost (GO):
Affected version(s) >=v11.5.0 <v11.5.5Fix Suggestion:
Update to version v11.5.5Related Resources (1)
Do you need more information?
Contact UsCVSS v4
Base Score:
6
Attack Vector
NETWORK
Attack Complexity
HIGH
Attack Requirements
NONE
Privileges Required
LOW
User Interaction
NONE
Vulnerable System Confidentiality
HIGH
Vulnerable System Integrity
NONE
Vulnerable System Availability
NONE
Subsequent System Confidentiality
NONE
Subsequent System Integrity
NONE
Subsequent System Availability
NONE
CVSS v3
Base Score:
5.3
Attack Vector
NETWORK
Attack Complexity
HIGH
Privileges Required
LOW
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
HIGH
Integrity
NONE
Availability
NONE
Weakness Type (CWE)
Exposure of Sensitive Information to an Unauthorized Actor
EPSS
Base Score:
0.19