CVE-2026-19603
Published:October 16, 2026
Updated:October 20, 2026
Mattermost versions 11.9.x <= 11.9.1, 11.8.x <= 11.8.5, 11.7.x <= 11.7.10, 11.10.x <= 11.10.1 fail to sanitize the active channel field returned by the user status API endpoints, which allows an authenticated user to learn the channel ID of a private channel another user is actively viewing via the status endpoints, without being a member of that channel. Mattermost Advisory ID: MMSA-2026-00765
Affected Packages
https://github.com/mattermost/mattermost.git (GITHUB):
Affected version(s) >=v11.7.0 <v11.7.11Fix Suggestion:
Update to version v11.7.11https://github.com/mattermost/mattermost.git (GITHUB):
Affected version(s) >=v11.10.0 <v11.10.2Fix Suggestion:
Update to version v11.10.2https://github.com/mattermost/mattermost.git (GITHUB):
Affected version(s) >=v11.9.0 <v11.9.2Fix Suggestion:
Update to version v11.9.2Related Resources (2)
Do you need more information?
Contact UsCVSS v4
Base Score:
5.3
Attack Vector
NETWORK
Attack Complexity
LOW
Attack Requirements
NONE
Privileges Required
LOW
User Interaction
NONE
Vulnerable System Confidentiality
LOW
Vulnerable System Integrity
NONE
Vulnerable System Availability
NONE
Subsequent System Confidentiality
NONE
Subsequent System Integrity
NONE
Subsequent System Availability
NONE
CVSS v3
Base Score:
4.3
Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
LOW
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
LOW
Integrity
NONE
Availability
NONE
Weakness Type (CWE)
Insertion of Sensitive Information Into Sent Data
EPSS
Base Score:
0.18