Mattermost 11.8.3 WebSocket Cmd Type Validation Leading to DoS
CVE-2026-10080 Published on August 17, 2026

Boards plugin panics on WebSocket command with non-string field types
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

Vendor Advisory NVD

Vulnerability Analysis

CVE-2026-10080 is exploitable with network access, and requires small amount of user privileges. This vulnerability is considered to have a low attack complexity. The potential impact of an exploit of this vulnerability is considered to have no impact on confidentiality and integrity, and a high impact on availability.

Attack Vector:
NETWORK
Attack Complexity:
LOW
Privileges Required:
LOW
User Interaction:
NONE
Scope:
UNCHANGED
Confidentiality Impact:
NONE
Integrity Impact:
NONE
Availability Impact:
HIGH

Weakness Type

Incorrect Type Conversion or Cast

The software does not correctly convert an object, resource, or structure from one type to a different type.


Products Associated with CVE-2026-10080

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Affected Versions

Mattermost: