EUVD-2026-16234

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 sanitize user-controlled post content in the mmctl commands terminal output which allows attackers to manipulate administrator terminals via crafted messages containing ANSI and OSC escape sequences...

EUVD-2026-16238

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...

EUVD-2026-16245

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...

EUVD-2026-16246

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...

GHSA-4765-V66X-RQX7 Mattermost doesn't set permissions on downloaded bulk export

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 doesn't set permissions on downloaded bulk export

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 allows system administrators to read arbitrary host files via malicious AdvancedLoggingJSON configuration

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...

EUVD-2026-16236

Mattermost Plugins versions =11.4 10.11.11.0 fail to validate webhook request timestamps which allows an attacker to corrupt Zoom meeting state in Mattermost via replayed webhook requests. Mattermost Advisory ID: MMSA-2026-00584...

GHSA-3MW5-466Q-295Q Mattermost allows system administrators to read arbitrary host files via malicious AdvancedLoggingJSON configuration

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...

EUVD-2026-16242

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...

EUVD-2026-16240

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...

GHSA-MPC7-MM28-F6WQ Mattermost allows authenticated guest users to enumerate user IDs outside their allowed visibility scope

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...

GHSA-3439-VQGJ-2GCF Mattermost allows attackers to manipulate administrator terminals via crafted messages containing ANSI and OSC escape sequences

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 sanitize user-controlled post content in the mmctl commands terminal output which allows attackers to manipulate administrator terminals via crafted messages containing ANSI and OSC escape sequences...

GHSA-VHGH-G7X8-4RX8 Mattermost doesn't validate decompressed archive entry sizes during file extraction

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...

Mattermost allows attackers to manipulate administrator terminals via crafted messages containing ANSI and OSC escape sequences

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 sanitize user-controlled post content in the mmctl commands terminal output which allows attackers to manipulate administrator terminals via crafted messages containing ANSI and OSC escape sequences...

CVE-2026-3115

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...

CVE-2026-3113

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...

CVE-2026-3112

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...

CVE-2026-3116

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...

CVE-2026-3114

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...