CVE-2026-3433
Received Received - Intake
Information Disclosure in Mattermost via WebSocket Events

Publication date: 2026-06-12

Last updated on: 2026-06-12

Assigner: Mattermost, Inc.

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 restrict role_updated websocket event broadcasts to members of the affected team or channel which allows an authenticated attacker with guest-level access to observe permission scheme change notifications for private teams they are not a member of via the websocket connection.. Mattermost Advisory ID: MMSA-2026-00616
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Published
2026-06-12
Last Modified
2026-06-12
Generated
2026-06-12
AI Q&A
2026-06-12
EPSS Evaluated
N/A
NVD
CVE-2026-3433
EUVD
EUVD-2026-36498
Affected Vendors & Products
Showing 4 associated CPEs
Vendor Product Version / Range
mattermost 11.6 to 11.6.1 (inc)
mattermost 11.5 to 11.5.4 (inc)
mattermost 10.11 to 10.11.15 (inc)
mattermost 10.11 to 10.11.16 (inc)
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Exploitability
CWE
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KEV
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CWE ID Description
CWE-200 The product exposes sensitive information to an actor that is not explicitly authorized to have access to that information.
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Impact Analysis

The impact of this vulnerability is that an attacker with guest-level access can gain unauthorized visibility into permission scheme change notifications for private teams they do not belong to.

This could lead to information disclosure about internal permission changes within private teams, potentially aiding further attacks or unauthorized access attempts.

Executive Summary

This vulnerability exists in certain versions of Mattermost (11.6.x <= 11.6.1, 11.5.x <= 11.5.4, and 10.11.x <= 10.11.16) where the system fails to restrict the broadcasting of role_updated websocket events to only members of the affected team or channel.

As a result, an authenticated attacker with guest-level access can observe permission scheme change notifications for private teams they are not a member of via the websocket connection.

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