CVE-2026-13417

Mattermost versions 11.9.x = 11.9.0, 11.8.x = 11.8.4, 11.7.x = 11.7.7, 10.11.x = 10.11.22 fail to validate the type of fields.properties on block creation which allows an authenticated user with editor access to a board to crash the Boards plugin worker and trigger a denial of service via a child...

CVE-2026-14259

Mattermost versions 11.9.x = 11.9.0, 11.8.x = 11.8.4, 11.7.x = 11.7.7, 10.11.x = 10.11.22 fail to enforce board creation permissions when importing archive files which allows an authenticated non-guest team member to create Open or Private boards despite administrator restrictions via importing a...

CVE-2026-15814

Mattermost versions 11.9.x = 11.9.0, 11.8.x = 11.8.4, 11.7.x = 11.7.7, 10.11.x = 10.11.22 fail to limit the amount of memory allocated when decoding uploaded image files which allows an authenticated user to cause excessive server memory consumption and potential denial of service via uploading a...

CVE-2026-12882

Mattermost versions 11.9.x = 11.9.0, 11.8.x = 11.8.4, 11.7.x = 11.7.7, 10.11.x = 10.11.22 fail to parse Markdown autolinks with unmatched trailing closing parentheses in linear time, which allows an authenticated user with permission to create posts to cause excessive server CPU consumption and...

CVE-2026-14344

Mattermost versions 11.9.x = 11.9.0, 11.8.x = 11.8.4, 11.7.x = 11.7.7, 10.11.x = 10.11.22 fail to enforce the board-creation permission which allows an unauthorized authenticated user to create boards via the board duplicate, boards-and-blocks, and archive-import endpoints.. Mattermost Advisory I...

CVE-2026-10542

Mattermost versions 11.9.x = 11.9.0, 11.8.x = 11.8.4, 11.7.x = 11.7.7, 10.11.x = 10.11.22 fail to validate channel action ownership which allows channel managers to update actions in other channels via the channel action update endpoint.. Mattermost Advisory ID: MMSA-2026-00692...

CVE-2026-10556

Mattermost versions 11.9.x = 11.9.0, 11.8.x = 11.8.4, 11.7.x = 11.7.7, 10.11.x = 10.11.22 fail to validate null entries in Microsoft Graph webhook notification payloads, which allows an unauthenticated attacker to crash the Microsoft Calendar plugin process and deny calendar integration service t...

CVE-2026-11993

Mattermost versions 11.9.x = 11.9.0, 11.8.x = 11.8.4, 11.7.x = 11.7.7, 10.11.x = 10.11.22 fail to properly enforce the limit of concurrent files being processed and handled failed files, which allows a user with permission to upload files to spawn more goroutines than intended and block the...

CVE-2026-10556 Unauthenticated webhook request with null notification entry could crash the Microsoft Calendar plugin.

Mattermost versions 11.9.x = 11.9.0, 11.8.x = 11.8.4, 11.7.x = 11.7.7, 10.11.x = 10.11.22 fail to validate null entries in Microsoft Graph webhook notification payloads, which allows an unauthenticated attacker to crash the Microsoft Calendar plugin process and deny calendar integration service t...

EUVD-2026-77379

Mattermost versions 11.9.x = 11.9.0, 11.8.x = 11.8.4, 11.7.x = 11.7.7, 10.11.x = 10.11.22 fail to validate null entries in Microsoft Graph webhook notification payloads, which allows an unauthenticated attacker to crash the Microsoft Calendar plugin process and deny calendar integration service t...

CVE-2026-10556 Unauthenticated webhook request with null notification entry could crash the Microsoft Calendar plugin.

Mattermost versions 11.9.x = 11.9.0, 11.8.x = 11.8.4, 11.7.x = 11.7.7, 10.11.x = 10.11.22 fail to validate null entries in Microsoft Graph webhook notification payloads, which allows an unauthenticated attacker to crash the Microsoft Calendar plugin process and deny calendar integration service t...

CVE-2026-10556

Mattermost versions 11.9.x ≤ 11.9.0, 11.8.x ≤ 11.8.4, 11.7.x ≤ 11.7.7, and 10.11.x ≤ 10.11.22 fail to validate null entries in Microsoft Graph webhook notification payloads. This allows an unauthenticated attacker to send a crafted POST request to the public webhook endpoint, crashing the Microso...

EUVD-2026-77376

Mattermost versions 11.9.x = 11.9.0, 11.8.x = 11.8.4, 11.7.x = 11.7.7, 10.11.x = 10.11.22 fail to validate the type of fields.properties on block creation which allows an authenticated user with editor access to a board to crash the Boards plugin worker and trigger a denial of service via a child...

CVE-2026-13417

Mattermost Boards plugin denial of service vulnerability in versions 11.9.x ≤ 11.9.0 , 11.8.x ≤ 11.8.4 , 11.7.x ≤ 11.7.7 , and 10.11.x ≤ 10.11.22 . The plugin fails to validate the type of fields.properties on block creation, allowing an authenticated user with editor access to a board to crash t...

CVE-2026-13417 Boards plugin denial of service via unvalidated block fields.properties

Mattermost versions 11.9.x = 11.9.0, 11.8.x = 11.8.4, 11.7.x = 11.7.7, 10.11.x = 10.11.22 fail to validate the type of fields.properties on block creation which allows an authenticated user with editor access to a board to crash the Boards plugin worker and trigger a denial of service via a child...

CVE-2026-13417 Boards plugin denial of service via unvalidated block fields.properties

Mattermost versions 11.9.x = 11.9.0, 11.8.x = 11.8.4, 11.7.x = 11.7.7, 10.11.x = 10.11.22 fail to validate the type of fields.properties on block creation which allows an authenticated user with editor access to a board to crash the Boards plugin worker and trigger a denial of service via a child...

CVE-2026-9812 Missing property field ownership validation in Playbooks run property update endpoint

Mattermost versions 11.9.x = 11.9.0, 11.8.x = 11.8.4, 11.7.x = 11.7.7, 10.11.x = 10.11.22 fail to validate that a property field belongs to the specified run before updating its value which allows an authenticated user with run property-management access to crash the Playbooks plugin via a REST...

EUVD-2026-77374

Mattermost versions 11.9.x = 11.9.0, 11.8.x = 11.8.4, 11.7.x = 11.7.7, 10.11.x = 10.11.22 fail to validate that a property field belongs to the specified run before updating its value which allows an authenticated user with run property-management access to crash the Playbooks plugin via a REST...

CVE-2026-9812

Mattermost versions 11.9.x ≤ 11.9.0, 11.8.x ≤ 11.8.4, 11.7.x ≤ 11.7.7, and 10.11.x ≤ 10.11.22 contain a missing validation flaw in the Playbooks plugin's run property update endpoint. The endpoint does not verify that a referenced property field belongs to the specified run before updating its va...

CVE-2026-9812 Missing property field ownership validation in Playbooks run property update endpoint

Mattermost versions 11.9.x = 11.9.0, 11.8.x = 11.8.4, 11.7.x = 11.7.7, 10.11.x = 10.11.22 fail to validate that a property field belongs to the specified run before updating its value which allows an authenticated user with run property-management access to crash the Playbooks plugin via a REST...