CVE-2026-19603
Received Received - Intake

Information Disclosure in Mattermost via Status API

Publication date: 2026-10-16

Last updated on: 2026-10-16

Assigner: Mattermost, Inc.

Description
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

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Meta Information

Published
2026-10-16
Last Modified
2026-10-16
Generated
2026-10-16
AI Q&A
2026-10-16
EPSS Evaluated
N/A
NVD
CVE-2026-19603
EUVD
EUVD-2026-102742

Affected Vendors & Products

Showing 4 associated CPEs
Vendor Product Version / Range
Mattermost Mattermost 11.9.0
Mattermost Mattermost 11.8.0
Mattermost Mattermost 11.7.0
Mattermost Mattermost 11.10.0

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-201 The code transmits data to another actor, but a portion of the data includes sensitive information that should not be accessible to that actor.

Attack-Flow Graph

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Executive Summary

This vulnerability affects Mattermost versions between 11.7.10 and 11.9.1, 11.8.5, and 11.10.1. It allows authenticated users to see the private channel ID another user is viewing through status API endpoints, even without being a member of that channel.

Impact Analysis

An attacker could exploit this to learn about private channels they are not supposed to access, potentially exposing sensitive discussions or data. This could lead to information leaks or unauthorized knowledge of internal communications.

Compliance Impact

This vulnerability could violate data protection regulations like GDPR or HIPAA by exposing private channel information to unauthorized users, potentially leading to unauthorized access to sensitive personal or health data.

Mitigation Strategies

Update Mattermost to a patched version (11.9.2 or later, 11.8.6 or later, 11.7.11 or later, 11.10.2 or later) to address the channel ID exposure issue.

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