Vulnerabilidades de Mattermost

Mattermost Plugins versions <=2.1.3.0 fail to limit the request body size on the {{/changes}} webhook endpoint which allows an authenticated attacker to cause memory exhaustion and denial of service via sending an oversized JSON payload. Mattermost Advisory ID: MMSA-2026-00611

Mattermost Plugins versions <=2.3.1 fail to limit the request body size on the {{/lifecycle}} webhook endpoint which allows an authenticated attacker to cause memory exhaustion and denial of service via sending an oversized JSON payload. Mattermost Advisory ID: MMSA-2026-00610

** UNSUPPORTED WHEN ASSIGNED ** Focalboard version 8.0 fails to validate file ownership when serving uploaded files. This allows an authenticated attacker who knows a victim's fileID to read the content of the file. NOTE: Focalboard as a standalone product is not maintained and no fix will be issued.

** UNSUPPORTED WHEN ASSIGNED ** Focalboard version 8.0 fails to sanitize category IDs before incorporating them into dynamic SQL statements when reordering categories. An attacker can inject a malicious SQL payload into the category id field, which is stored in the database and later executed unsanitized when the category reorder API processes the stored value. This Second-Order SQL Injection (Time-Based Blind) allows an authenticated attacker to exfiltrate sensitive data including password hashes of other users. NOTE: Focalboard as a standalone product is not maintained and no fix will be issued.

Mattermost Plugins versions <=11.4 11.0.4 11.1.3 11.3.2 10.11.11.0 fail to validate incoming request size which allows an authenticated attacker to cause service disruption via the webhook endpoint. Mattermost Advisory ID: MMSA-2026-00589

Mattermost versions 11.2.x <= 11.2.2, 10.11.x <= 10.11.10, 11.4.x <= 11.4.0, 11.3.x <= 11.3.1 fail to apply view restrictions when retrieving group member IDs, which allows authenticated guest users to enumerate user IDs outside their allowed visibility scope via the group retrieval endpoint.. Mattermost Advisory ID: MMSA-2026-00594

Mattermost versions 11.4.x <= 11.4.0, 11.3.x <= 11.3.1, 11.2.x <= 11.2.3, 10.11.x <= 10.11.11 fail to validate decompressed archive entry sizes during file extraction which allows authenticated users with file upload permissions to cause a denial of service via crafted zip archives containing highly compressed entries (zip bombs) that exhaust server memory.. Mattermost Advisory ID: MMSA-2026-00598

Mattermost versions 11.4.x <= 11.4.0, 11.3.x <= 11.3.1, 11.2.x <= 11.2.3, 10.11.x <= 10.11.11 fail to set permissions on downloaded bulk export which allows other local users on the server to be able to read contents of the bulk export.. Mattermost Advisory ID: MMSA-2026-00593

Mattermost versions 11.4.x <= 11.4.0, 11.3.x <= 11.3.1, 11.2.x <= 11.2.3, 10.11.x <= 10.11.11 fail to validate Advanced Logging file target paths which allows system administrators to read arbitrary host files via malicious AdvancedLoggingJSON configuration in support packet generation. Mattermost Advisory ID: MMSA-2025-00562

Mattermost versions 11.2.x <= 11.2.2, 10.11.x <= 10.11.10, 11.4.x <= 11.4.0, 11.3.x <= 11.3.1 fail to restrict team-level access when processing membership sync from a remote cluster, which allows a malicious remote cluster to grant a user access to an entire private team instead of only the shared channel via sending crafted membership sync messages that trigger team membership assignment. Mattermost Advisory ID: MMSA-2026-00574

Mattermost versions 11.2.x <= 11.2.2, 10.11.x <= 10.11.10, 11.4.x <= 11.4.0, 11.3.x <= 11.3.1 fail to properly validate CSRF tokens in the /api/v4/access_control_policies/{policy_id}/activate endpoint, which allows an attacker to trick an admin into changing access control policy active status via a crafted request.. Mattermost Advisory ID: MMSA-2026-00578

Mattermost versions 11.4.x <= 11.4.0, 11.3.x <= 11.3.1, 11.2.x <= 11.2.3, 10.11.x <= 10.11.11 fail to properly validate user identity in the OpenID {{IsSameUser()}} comparison logic, which allows an attacker to take over arbitrary user accounts via an overly permissive substring matching flaw in the user discovery flow.. Mattermost Advisory ID: MMSA-2026-00590

Mattermost versions 11.4.x <= 11.4.0, 11.3.x <= 11.3.1, 11.2.x <= 11.2.3, 10.11.x <= 10.11.11 fail to rate limit login requests which allows unauthenticated remote attackers to cause denial of service (server crash and restart) via HTTP/2 single packet attack with 100+ parallel login requests.. Mattermost Advisory ID: MMSA-2025-00566

Mattermost versions 10.11.x <= 10.11.10 Fail to invalidate cached permalink preview data when a user loses channel access which allows the user to continue viewing private channel content via previously cached permalink previews until cache reset or relogin.. Mattermost Advisory ID: MMSA-2026-00580

Mattermost versions 11.3.x <= 11.3.0, 11.2.x <= 11.2.2 fail to verify run_create permission for empty playbookId, which allows team members to create unauthorized runs via the playbook run API. Mattermost Advisory ID: MMSA-2025-00542

Mattermost versions 11.3.x <= 11.3.0, 11.2.x <= 11.2.2, 10.11.x <= 10.11.10 fail to canonicalize IPv4-mapped IPv6 addresses before reserved IP validation which allows an attacker to perform SSRF attacks against internal services via IPv4-mapped IPv6 literals (e.g., [::ffff:127.0.0.1]).. Mattermost Advisory ID: MMSA-2026-00585

Mattermost versions 11.3.x <= 11.3.0, 11.2.x <= 11.2.2, 10.11.x <= 10.11.10 fail to properly enforce read permissions in search API endpoints which allows guest users without read permissions to access posts and files in channels via search API requests. Mattermost Advisory ID: MMSA-2025-00554

Mattermost versions 11.3.x <= 11.3.0, 11.2.x <= 11.2.2, 10.11.x <= 10.11.10 fail to use consistent error responses when handling the /mute command which allows an authenticated team member to enumerate private channels they are not authorized to know about via differing error messages for nonexistent versus private channels. Mattermost Advisory ID: MMSA-2026-00588