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

Project Subscriptions

Vendors Products
Mattermost Subscribe
Mattermost Subscribe
Advisories

No advisories yet.

Fixes

Solution

Update Mattermost to versions 11.9.0, 11.7.7, 10.11.22, 11.8.4 or higher.


Workaround

No workaround given by the vendor.

References
History

Mon, 17 Aug 2026 23:45:00 +0000

Type Values Removed Values Added
First Time appeared Mattermost
Mattermost mattermost
Vendors & Products Mattermost
Mattermost mattermost

Mon, 17 Aug 2026 22:15:00 +0000

Type Values Removed Values Added
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
Title Boards plugin panics on WebSocket command with non-string field types
Weaknesses CWE-704
References
Metrics cvssV3_1

{'score': 6.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H'}


Projects

Sign in to view the affected projects.

cve-icon MITRE

Status: PUBLISHED

Assigner: Mattermost

Published:

Updated: 2026-08-17T22:04:30.830Z

Reserved: 2026-05-29T10:40:50.902Z

Link: CVE-2026-10080

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-08-17T22:16:58.607

Modified: 2026-08-17T22:16:58.607

Link: CVE-2026-10080

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-08-17T23:30:04Z

Weaknesses