CVE-2026-5139

Mattermost plugin vulnerability CVE-2026-5139 affects Mattermost versions 11.7.x ≤ 11.7.0, 11.6.x ≤ 11.6.2, 11.5.x ≤ 11.5.5, 10.11.x ≤ 10.11.17. The issue arises in the /gitlab connect command handler where administrator authorization is not enforced for the setDefaultInstance call, allowing any ...

CVE-2026-5139 GitLab Plugin Allows Non-Admin Users to Modify Default Instance Configuration

Mattermost versions 11.7.x slash command.. Mattermost Advisory ID: MMSA-2026-00644...

EUVD-2026-38246

Mattermost versions 11.7.x slash command.. Mattermost Advisory ID: MMSA-2026-00644...

CVE-2026-5139 GitLab Plugin Allows Non-Admin Users to Modify Default Instance Configuration

Mattermost versions 11.7.x slash command.. Mattermost Advisory ID: MMSA-2026-00644...

PT-2026-51322

Name of the Vulnerable Software and Affected Versions Mattermost versions 10.11.x through 10.11.17 Mattermost versions 11.5.x through 11.5.5 Mattermost versions 11.6.x through 11.6.2 Mattermost versions 11.7.x through 11.7.0 Description An issue exists where the system fails to invalidate cached...

PT-2026-51304

Name of the Vulnerable Software and Affected Versions Mattermost version 11.7.0 Mattermost version 11.6.2 Mattermost version 11.5.5 Mattermost version 10.11.17 Description Improper authorization in the GitLab connect command handler allows any authenticated user to overwrite the global default...

PT-2026-51316

Name of the Vulnerable Software and Affected Versions Mattermost version 11.7.0 Mattermost version 11.6.2 Mattermost version 11.5.5 Mattermost version 10.11.17 Description Remote unauthenticated attackers can inject a rogue sharedSecret and disrupt the Jira integration. This occurs during the...

PT-2026-51314

Name of the Vulnerable Software and Affected Versions Mattermost version 11.7.0 Mattermost version 11.6.2 Mattermost version 11.5.5 Mattermost version 10.11.17 Description An issue exists where the system fails to validate channel ownership of an existing subscription before applying edits. This...

Mattermost Server 10.11.x < 10.11.14 / 11.5.x < 11.5.2 Vulnerability (MMSA-2025-00552)

The version of Mattermost Server installed on the remote host is affected by a vulnerability: - Mattermost fails to check if teamid was being changed when updating playbooks, allowing users with only Manage Playbook Configurations permission to change a playbook's team, bypassing manage members...

Mattermost Desktop 5.13.x < 5.13.6 / 6.x < 6.2.0 Multiple Vulnerabilities (MMSA-2026-00651 / MMSA-2026-00652)

The version of Mattermost Desktop installed on the remote host is affected by multiple vulnerabilities: - Mattermost Desktop App versions =6.1 5.5.13.0 fail to restrict the allow list of domains to which NTLM credentials were forwarded to in the Mattermost Desktop App which allows any user on a...

Mattermost Server 10.11.x < 10.11.14 / 11.4.x < 11.4.4 / 11.5.x < 11.5.2 Vulnerability (MMSA-2026-00597)

The version of Mattermost Server installed on the remote host is affected by a vulnerability: - Mattermost fails to enforce slash command trigger-word uniqueness during command updates which allows an authenticated team member with Manage Own Slash Commands permission to hijack and impersonate...

CVE-2026-8683

Mattermost Desktop App versions =6.1 5.5.13.0 fail to account for attempting to open extremely long URLs in the Mattermost Desktop App which allows a malicious server owner to crash the application via including a script to call window.open on a very large URL. Mattermost Advisory ID:...

CVE-2026-6517

Mattermost Desktop App versions =6.1 5.5.13.0 fail to restrict the allow list of domains to which NTLM credentials were forwarded to in the Mattermost Desktop App which allows any user on a server without the image proxy enabled to intercept other users credentials via embedding an image that...

EUVD-2026-36732

Mattermost Desktop App versions =6.1 5.5.13.0 fail to account for attempting to open extremely long URLs in the Mattermost Desktop App which allows a malicious server owner to crash the application via including a script to call window.open on a very large URL. Mattermost Advisory ID:...

CVE-2026-8683 Overly long URLs crash the Mattermost Desktop App

Mattermost Desktop App versions =6.1 5.5.13.0 fail to account for attempting to open extremely long URLs in the Mattermost Desktop App which allows a malicious server owner to crash the application via including a script to call window.open on a very large URL. Mattermost Advisory ID:...

CVE-2026-8683

Mattermost Desktop App

CVE-2026-8683 Overly long URLs crash the Mattermost Desktop App

Mattermost Desktop App versions =6.1 5.5.13.0 fail to account for attempting to open extremely long URLs in the Mattermost Desktop App which allows a malicious server owner to crash the application via including a script to call window.open on a very large URL. Mattermost Advisory ID:...

CVE-2026-6517 Mattermost Desktop App fails to restrict the allow list of domains which NTLM credentials are passed

Mattermost Desktop App versions =6.1 5.5.13.0 fail to restrict the allow list of domains to which NTLM credentials were forwarded to in the Mattermost Desktop App which allows any user on a server without the image proxy enabled to intercept other users credentials via embedding an image that...

CVE-2026-6517 Mattermost Desktop App fails to restrict the allow list of domains which NTLM credentials are passed

Mattermost Desktop App versions =6.1 5.5.13.0 fail to restrict the allow list of domains to which NTLM credentials were forwarded to in the Mattermost Desktop App which allows any user on a server without the image proxy enabled to intercept other users credentials via embedding an image that...

CVE-2026-6517 Mattermost Desktop App fails to restrict the allow list of domains which NTLM credentials are passed

Mattermost Desktop App versions =6.1 5.5.13.0 fail to restrict the allow list of domains to which NTLM credentials were forwarded to in the Mattermost Desktop App which allows any user on a server without the image proxy enabled to intercept other users credentials via embedding an image that...