Detections
Analytics

Mattermost Server 10.5.x <= 10.5.12 / 10.11.x <= 10.11.4 / 10.12.x <= 10.12.1 / 11.0.x <= 11.0.2 Multiple Vulnerabilities (CVE-2025-12421, MMSA-2025-00526, CVE-2025-12756)

critical Nessus Plugin ID 278109

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Synopsis

The remote host is missing a security update.

Description

The version of Mattermost Server installed on the remote host is affected by a vulnerability as referenced in CVE-2025-12421, MMSA-2025-00526 and CVE-2025-12756.

 - Mattermost versions 11.0.x <= 11.0.2, 10.12.x <= 10.12.1, 10.11.x <= 10.11.4, 10.5.x <= 10.5.12 fail to to verify that the token used during the code exchange originates from the same authentication flow, which allows an authenticated user to perform account takeover via a specially crafted email address used when switching authentication methods and sending a request to the /users/login/sso/code-exchange endpoint. The vulnerability requires ExperimentalEnableAuthenticationTransfer to be enabled (default: enabled) and RequireEmailVerification to be disabled (default: disabled). (CVE-2025-12421)
- Mattermost versions 11.0.x <= 11.0.2, 10.12.x <= 10.12.1, 10.11.x <= 10.11.4, 10.5.x <= 10.5.12 fail to sanitize team email addresses to be visible only to Team Admins, which allows any authenticated user to view team email addresses via the GET /api/v4/channels/{channel_id}/common_teams endpoint (CVE-2025-12559)
- Mattermost versions 11.0.x <= 11.0.2, 10.12.x <= 10.12.1, 10.11.x <= 10.11.4, 10.5.x <= 10.5.12 fail to validate user permissions when deleting comments in Boards, which allows an authenticated user with the editor role to delete comments created by other users.
 (CVE-2025-12756)

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

Solution

Upgrade to Mattermost Server version 10.5.13, 10.11.5, 10.12.2, 11.0.3, 11.1.0 or later.

See Also

https://mattermost.com/security-updates/

Plugin Details

Severity: Critical

ID: 278109

File Name: mattermost_server_MMSA-2025-00526.nasl

Version: 1.2

Type: remote

Family: CGI abuses

Published: 12/10/2025

Updated: 12/12/2025

Supported Sensors: Nessus

Risk Information

VPR

Risk Factor: High

Score: 7.3

CVSS v3

Risk Factor: Critical

Base Score: 9.9

Vector: CVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H

Vulnerability Information

CPE: cpe:/a:mattermost:mattermost_server

Required KB Items: installed_sw/Mattermost Server

Patch Publication Date: 10/31/2025

Vulnerability Publication Date: 10/31/2025

Reference Information

CVE: CVE-2025-12421, CVE-2025-12559, CVE-2025-12756

IAVA: 2025-A-0893