CVE-2026-10080

Received Received - Intake

Denial of Service in Mattermost via WebSocket Command

Publication date: 2026-08-17

Last updated on: 2026-08-17

Assigner: Mattermost, Inc.

Description

Mattermost versions 11.7.x <= 11.7.6, 10.11.x <= 10.11.21, 11.8.x <= 11.8.3 fails to validate WebSocket command field types which allows an authenticated user to crash the plugin process and deny service to all Boards users via a custom_focalboard_SUBSCRIBE_TEAM message with a non-string teamId.. Mattermost Advisory ID: MMSA-2026-00687

CVSS Scores

EPSS Scores

Probability:
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Meta Information

Published

2026-08-17

Last Modified

2026-08-17

Generated

2026-08-18

AI Q&A

2026-08-18

EPSS Evaluated

N/A

NVD

CVE-2026-10080

EUVD

EUVD-2026-60539

Affected Vendors & Products

Vendor	Product	Version / Range
mattermost	mattermost	to 11.7.6 (inc)
mattermost	mattermost	to 10.11.21 (inc)
mattermost	mattermost	to 11.8.3 (inc)

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-704	The product does not correctly convert an object, resource, or structure from one type to a different type.

Attack-Flow Graph

Executive Summary

This vulnerability affects Mattermost versions between 11.7.0 and 11.7.6, 10.11.0 and 10.11.21, and 11.8.0 and 11.8.3. It allows an authenticated user to send a malformed WebSocket message with a non-string teamId field to crash the plugin process. This denial-of-service condition prevents all Boards users from accessing the service.

Detection Guidance

Detecting this vulnerability requires checking Mattermost server logs for malformed WebSocket SUBSCRIBE_TEAM messages with non-string teamId fields. Monitor for crashes in the Boards plugin process or service disruptions to users.

Impact Analysis

If you use a vulnerable Mattermost version, an attacker with valid credentials could disrupt service for all Boards users by sending a specially crafted WebSocket message. This would make the Boards feature unavailable until the server is restarted or the issue is resolved.

Compliance Impact

The vulnerability causes a denial of service for Boards users by crashing the plugin process, which could disrupt access to critical data. This may impact compliance with GDPR or HIPAA if it leads to prolonged unavailability of personal or health data, potentially violating availability requirements.

Mitigation Strategies

Upgrade Mattermost to a patched version (11.7.7+, 10.11.22+, or 11.8.4+) immediately. If upgrading is not possible, restrict authenticated user access to Boards features or disable the Boards plugin until patched.

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