Github.Com Mattermost Mattermost Server V8 vulnerabilities

CVE-2025-14350 [MEDIUM] CWE-862 Mattermost fails to properly validate team membership when processing channel mentions Mattermost fails to properly validate team membership when processing channel mentions Mattermost versions 11.1.x <= 11.1.2, 10.11.x <= 10.11.9, 11.2.x <= 11.2.1 fail to properly validate team membership when processing channel mentions which allows authenticated users to determine the existence of teams and their URL names via posting channel shortlinks and observing the chann

CVE-2025-11777 [LOW] CWE-863 Mattermost Incorrect Authorization vulnerability Mattermost Incorrect Authorization vulnerability Mattermost versions 10.11.x <= 10.11.3, 10.5.x <= 10.5.11 fail to properly validate team membership permissions in the Add Channel Member API, which allows users from one team to access user metadata and channel membership information from other teams via the API endpoint.

CVE-2025-12756 [MEDIUM] CWE-863 Mattermost fails to validate user permissions when deleting comments in Boards Mattermost fails to validate user permissions when deleting comments in Boards 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-2026-3495 [LOW] CWE-79 Mattermost doesn't escape some variables that could contain malicious content during error page composition Mattermost doesn't escape some variables that could contain malicious content during error page composition Mattermost versions 11.5.x <= 11.5.1, 10.11.x <= 10.11.13 fail to escape some variables that could contain malicious content during error page composition which allows an attacker with access to edit some site configuration to execute some malicious code v

CVE-2025-9078 [MEDIUM] CWE-328 Mattermost makes Use of Weak Hash Mattermost makes Use of Weak Hash Mattermost versions 10.8.x <= 10.8.3, 10.5.x <= 10.5.8, 9.11.x <= 9.11.17, 10.10.x <= 10.10.1, 10.9.x <= 10.9.3 fail to properly validate cache keys for link metadata which allows authenticated users to access unauthorized posts and poison link previews via hash collision attacks on FNV-1 hashing.

CVE-2024-1953 [MEDIUM] CWE-400 Mattermost fails to limit the number of role names Mattermost fails to limit the number of role names Mattermost versions 8.1.x before 8.1.9, 9.2.x before 9.2.5, 9.3.0, and 9.4.x before 9.4.2 fail to limit the number of role names requested from the API, allowing an authenticated attacker to cause the server to run out of memory and crash by issuing an unusually large HTTP request.

CVE-2023-6202 [MEDIUM] CWE-284 Mattermost Improper Access Control vulnerability Mattermost Improper Access Control vulnerability Mattermost fails to perform proper authorization in the `/plugins/focalboard/api/v2/users` endpoint allowing an attacker who is a guest user and knows the ID of another user to get their information (e.g. name, surname, nickname) via Mattermost Boards.

CVE-2024-1887 [HIGH] CWE-284 Mattermost post fetching without auditing in compliance export Mattermost post fetching without auditing in compliance export Mattermost fails to check if compliance export is enabled when fetching posts of public channels allowing a user that is not a member of the public channel to fetch the posts, which will not be audited in the compliance export.

CVE-2024-24776 [LOW] CWE-284 Mattermost fails to check the required permissions Mattermost fails to check the required permissions Mattermost fails to check the required permissions in the POST /api/v4/channels/stats/member_count API resulting in channel member counts being leaked to a user without permissions.

CVE-2025-24526 [MEDIUM] CWE-863 Mattermost fails to restrict channel export of archived channels Mattermost fails to restrict channel export of archived channels Mattermost versions 10.1.x <= 10.1.3, 10.4.x <= 10.4.1, 9.11.x <= 9.11.7, 10.3.x <= 10.3.2, 10.2.x <= 10.2.2 fail to restrict channel export of archived channels when the "Allow users to view archived channels" is disabled which allows a user to export channel contents when they shouldn't have access to it

CVE-2026-26246 [MEDIUM] CWE-789 Mattermost fails to bound memory allocation when processing PSD image files Mattermost fails to bound memory allocation when processing PSD image files Mattermost versions 11.3.x <= 11.3.0, 11.2.x <= 11.2.2, 10.11.x <= 10.11.10 fail to bound memory allocation when processing PSD image files which allows an authenticated attacker to cause server memory exhaustion and denial of service via uploading a specially crafted PSD file. Mattermost Advisory ID: MMSA-2026-00

CVE-2026-2578 [MEDIUM] CWE-201 Mattermost fails to preserve the redacted state of burn-on-read posts during deletion Mattermost fails to preserve the redacted state of burn-on-read posts during deletion Mattermost versions 11.3.x <= 11.3.0 fail to preserve the redacted state of burn-on-read posts during deletion which allows channel members to access unrevealed burn-on-read message contents via the WebSocket post deletion event. Mattermost Advisory ID: MMSA-2026-00579

CVE-2025-27571 [MEDIUM] CWE-863 Mattermost Incorrect Authorization vulnerability Mattermost Incorrect Authorization vulnerability Mattermost versions 10.5.x <= 10.5.1, 10.4.x <= 10.4.3, 9.11.x <= 9.11.9 fail to check the "Allow Users to View Archived Channels" configuration when fetching channel metadata of a post from archived channels, which allows authenticated users to access such information when a channel is archived.

CVE-2025-24920 [MEDIUM] CWE-863 Mattermost Fails to Restrict Bookmark Creation and Updates in Archived Channels Mattermost Fails to Restrict Bookmark Creation and Updates in Archived Channels Mattermost versions 10.4.x <= 10.4.2, 10.3.x <= 10.3.3, 9.11.x <= 9.11.8, 10.5.x <= 10.5.0 fail to restrict bookmark creation and updates in archived channels, which allows authenticated users created or update bookmarked in archived channels

CVE-2025-3227 [MEDIUM] CWE-863 Mattermost allows unauthorized channel member management through playbook runs Mattermost allows unauthorized channel member management through playbook runs Mattermost versions 10.5.x <= 10.5.5, 9.11.x <= 9.11.15, 10.8.x <= 10.8.0, 10.7.x <= 10.7.2, 10.6.x <= 10.6.5 fail to properly enforce channel member management permissions in playbook runs, allowing authenticated users without the 'Manage Channel Members' permission to add or remove users from public and pri

CVE-2025-3446 [MEDIUM] CWE-863 Mattermost Fails to Validate Team Invite Permissions Mattermost Fails to Validate Team Invite Permissions Mattermost versions 10.6.x <= 10.6.1, 10.5.x <= 10.5.2, 10.4.x <= 10.4.4, 9.11.x <= 9.11.11 fail to check the correct permissions which allows authenticated users who only have permission to invite non-guest users to a team to add guest users to that team via the API to add a single user to a team.

CVE-2025-27933 [MEDIUM] CWE-863 Mattermost allows members with permission to convert public channels to private and convert private to public Mattermost allows members with permission to convert public channels to private and convert private to public Mattermost versions 10.4.x <= 10.4.2, 10.3.x <= 10.3.3, 9.11.x <= 9.11.8 fail to to enforce channel conversion restrictions, which allows members with permission to convert public channels to private ones to also convert private ones to public.

CVE-2026-21386 [MEDIUM] CWE-203 Mattermost fails to use consistent error responses when handling the /mute command Mattermost fails to use consistent error responses when handling the /mute command 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

CVE-2026-6339 [MEDIUM] CWE-346 Mattermost doesn't validate the X-Requested-With header on the burn-on-read reveal endpoint Mattermost doesn't validate the X-Requested-With header on the burn-on-read reveal endpoint Mattermost versions 11.5.x <= 11.5.1, 11.4.x <= 11.4.3 fail to validate the X-Requested-With header on the burn-on-read reveal endpoint which allows an authenticated channel member to force the reveal of a burn-on-read message without recipient consent via a crafted Markdown image ta

CVE-2023-5967 [MEDIUM] CWE-754 Mattermost denial of service vulnerability Mattermost denial of service vulnerability Mattermost fails to properly validate requests to the Calls plugin, allowing an attacker sending a request without a User Agent header to cause a panic and crash the Calls plugin