Vulnerabilities (CVE)

Mattermost versions 10.11.x <= 10.11.9 fail to properly validate channel membership at the time of data retrieval which allows a deactivated user to learn team names they should not have access to via a race condition in the /common_teams API endpoint.. Mattermost Advisory ID: MMSA-2025-00549

Mattermost versions 11.1.x <= 11.1.2, 10.11.x <= 10.11.9, 11.2.x <= 11.2.1 fail to sanitize sensitive data in WebSocket messages which allows authenticated users to exfiltrate password hashes and MFA secrets via profile nickname updates or email verification events. Mattermost Advisory ID: MMSA-2025-00560

Mattermost versions 11.1.x <= 11.1.2, 10.11.x <= 10.11.9, 11.2.x <= 11.2.1 fail to validate user permissions when creating Jira issues from Mattermost posts, which allows an authenticated attacker with access to the Jira plugin to read post content and attachments from channels they do not have access to via the /create-issue API endpoint by providing the post ID of an inaccessible post.. Mattermost Advisory ID: MMSA-2025-00550

Mattermost versions 11.1.x <= 11.1.2, 10.11.x <= 10.11.9, 11.2.x <= 11.2.1 and Mattermost Plugin Zoom versions <=1.11.0 fail to validate the authenticated user when processing {{/plugins/zoom/api/v1/channel-preference}}, which allows any logged-in user to change Zoom meeting restrictions for arbitrary channels via crafted API requests.. Mattermost Advisory ID: MMSA-2025-00558

Mattermost versions 11.1.x <= 11.1.2, 10.11.x <= 10.11.9, 11.2.x <= 11.2.1 and Mattermost Plugin Zoom versions <=1.11.0 fail to validate user identity and post ownership in the {{/api/v1/askPMI}} endpoint which allows unauthorized users to start Zoom meetings as any user and overwrite arbitrary posts via direct API calls with manipulated user IDs and post data.. Mattermost Advisory ID: MMSA-2025-00534

Mattermost versions 11.1.x <= 11.1.2, 10.11.x <= 10.11.9, 11.2.x <= 11.2.1 fail to properly validate login method restrictions which allows an authenticated user to bypass SSO-only login requirements via userID-based authentication. Mattermost Advisory ID: MMSA-2025-00548

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 channel_mentions property in the API response. Mattermost Advisory ID: MMSA-2025-00563

Mattermost versions 10.11.x <= 10.11.9 fail to enforce invite permissions when updating team settings, which allows team administrators without proper permissions to bypass restrictions and add users to their team via API requests. Mattermost Advisory ID: MMSA-2025-00561

Mattermost versions 10.11.x <= 10.11.8 fail to validate input size before processing hashtags which allows an authenticated attacker to exhaust CPU resources via a single HTTP request containing a post with thousands space-separated tokens

Mattermost versions 10.11.x <= 10.11.8, 11.1.x <= 11.1.1, 11.0.x <= 11.0.6 fail to prevent infinite re-renders on API errors which allows authenticated users to cause application-level DoS via triggering unbounded component re-render loops.

Mattermost Plugin MSTeams versions <2.1.0 and Mattermost Server versions 10.5.x <=10.5.1 with the MS Teams plugin enabled fail to perform constant time comparison on a MSTeams plugin webhook secret which allows an attacker to retrieve the webhook secret of the MSTeams plugin via a timing attack during webhook secret comparison.

Mattermost versions 11.1.x <= 11.1.0, 11.0.x <= 11.0.5, 10.12.x <= 10.12.3, 10.11.x <= 10.11.7 fails to validate user channel membership when attaching Mattermost posts as comments to Jira issues, which allows an authenticated attacker with access to the Jira plugin to read post content and attachments from channels they do not have access to.

Mattermost versions 11.1.x <= 11.1.0, 11.0.x <= 11.0.5, 10.12.x <= 10.12.3, 10.11.x <= 10.11.7 fail to verify that post actions invoking /share-issue-publicly were created by the Jira plugin which allowed a malicious Mattermost user to exfiltrate Jira tickets when victim users interacted with affected posts

Mattermost versions 10.11.x <= 10.11.4 fail to validate redirect URLs on the /error page, which allows an attacker to redirect a victim to a malicious site via a crafted link opened in a new tab.

Mattermost versions 11.0.x <= 11.0.4, 10.12.x <= 10.12.2, 10.11.x <= 10.11.6 and Mattermost Calls versions <=1.10.0 fail to implement CSRF protection on the Calls widget page which allows an authenticated attacker to initiate calls and inject messages into channels or direct messages via a malicious webpage or crafted link

Mattermost versions 10.11.x <= 10.11.6 and Mattermost GitHub plugin versions <=2.4.0 fail to validate plugin bot identity in reaction forwarding which allows attackers to hijack the GitHub reaction feature to make users add reactions to arbitrary GitHub objects via crafted notification posts.

Mattermost versions 11.1.x <= 11.1.0, 11.0.x <= 11.0.5, 10.12.x <= 10.12.3, 10.11.x <= 10.11.7 with the Jira plugin enabled and Mattermost Jira plugin versions <=4.4.0 fail to enforce authentication and issue-key path restrictions in the Jira plugin, which allows an unauthenticated attacker who knows a valid user ID to issue authenticated GET and POST requests to the Jira server via crafted plugin payloads that spoof the user ID and inject arbitrary issue key paths. Mattermost Advisory ID: MMSA- ... Mattermost versions 11.1.x <= 11.1.0, 11.0.x <= 11.0.5, 10.12.x <= 10.12.3, 10.11.x <= 10.11.7 with the Jira plugin enabled and Mattermost Jira plugin versions <=4.4.0 fail to enforce authentication and issue-key path restrictions in the Jira plugin, which allows an unauthenticated attacker who knows a valid user ID to issue authenticated GET and POST requests to the Jira server via crafted plugin payloads that spoof the user ID and inject arbitrary issue key paths. Mattermost Advisory ID: MMSA-2025-00555

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Mattermost versions 10.11.x <= 10.11.5, 11.0.x <= 11.0.4, 10.12.x <= 10.12.2 fail to invalidate remote cluster invite tokens when using the legacy (version 1) protocol or when the confirming party does not provide a refreshed token, which allows an attacker who has obtained an invite token to authenticate as the remote cluster and perform limited actions on shared channels even after the invitation has been legitimately confirmed.

Mattermost versions 11.0.x <= 11.0.4, 10.12.x <= 10.12.2, 10.11.x <= 10.11.6 fail to check WebSocket request field for proper UTF-8 format, which allows attacker to crash Calls plug-in via sending malformed request.

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.

Mattermost versions 10.11.x <= 10.11.4, 10.5.x <= 10.5.12 fail to validate the user permission when accessing the files and subscribing to the block in Boards, which allows an authenticated user to access other board files and was able to subscribe to the block from other boards that the user does not have access to

Mattermost versions 10.12.x <= 10.12.1, 10.11.x <= 10.11.4, 10.5.x <= 10.5.12, 11.0.x <= 11.0.3 fail to properly validate OAuth state tokens during OpenID Connect authentication which allows an authenticated attacker with team creation privileges to take over a user account via manipulation of authentication data during the OAuth completion flow. This requires email verification to be disabled (default: disabled), OAuth/OpenID Connect to be enabled, and the attacker to control two users in the S ... Mattermost versions 10.12.x <= 10.12.1, 10.11.x <= 10.11.4, 10.5.x <= 10.5.12, 11.0.x <= 11.0.3 fail to properly validate OAuth state tokens during OpenID Connect authentication which allows an authenticated attacker with team creation privileges to take over a user account via manipulation of authentication data during the OAuth completion flow. This requires email verification to be disabled (default: disabled), OAuth/OpenID Connect to be enabled, and the attacker to control two users in the SSO system with one of them never having logged into Mattermost.

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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

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 ... 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).

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Mattermost versions 10.11.x <= 10.11.3, 10.5.x <= 10.5.11 fail to enforce access permissions on the Agents plugin which allows other users to determine when users had read channels via channel member objects

Mattermost versions 10.11.x <= 10.11.3, 10.5.x <= 10.5.11, 10.12.x <= 10.12.0 fail to validate the relationship between the post being updated and the MSTeams plugin OAuth flow which allows an attacker to edit arbitrary posts via a crafted MSTeams plugin OAuth redirect URL.

Mattermost versions 10.11.x <= 10.11.3, 10.5.x <= 10.5.11, 10.12.x <= 10.12.0 fail to sanitize user data which allows system administrators to access password hashes and MFA secrets via the POST /api/v4/users/{user_id}/email/verify/member endpoint

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

Mattermost versions <11 fail to properly restrict access to archived channel search API which allows guest users to discover archived public channels via the `/api/v4/teams/{team_id}/channels/search_archived` endpoint

Mattermost versions <11.0 fail to properly enforce the "Allow users to view archived channels" setting which allows regular users to access archived channel content and files via the "Open in Channel" functionality from followed threads

Mattermost versions <11 fail to enforce multi-factor authentication on WebSocket connections which allows unauthenticated users to access sensitive information via WebSocket events

Mattermost Server versions 10.5.x <= 10.5.9 utilizing the Agents plugin fail to reject empty request bodies which allows users to trick users into clicking malicious links via post actions

Mattermost versions 10.5.x <= 10.5.12, 10.11.x <= 10.11.2 fail to properly validate guest user permissions when accessing channel information which allows guest users to discover active public channels and their metadata via the `/api/v4/teams/{team_id}/channels/ids` endpoint

Mattermost versions 10.5.x <= 10.5.10, 10.11.x <= 10.11.2 fail to properly validate guest user permissions when adding channel members which allows guest users to add any team members to their private channels via the `/api/v4/channels/{channel_id}/members` endpoint

Mattermost versions 10.10.x <= 10.10.2, 10.5.x <= 10.5.10, 10.11.x <= 10.11.2 fail to validate email ownership during Slack import process which allows attackers to create verified user accounts with arbitrary email domains via malicious Slack import data to bypass email-based team access restrictions

Mattermost versions 10.5.x <= 10.5.10, 10.11.x <= 10.11.2 fail to use constant-time comparison for sensitive string comparisons which allows attackers to exploit timing oracles to perform byte-by-byte brute force attacks via response time analysis on Cloud API keys and OAuth client secrets

Mattermost versions 10.11.x <= 10.11.1, 10.10.x <= 10.10.2, 10.5.x <= 10.5.10 fail to verify a user has permission to join a Mattermost team using the original invite token which allows any attacked to join any team on a Mattermost server regardless of restrictions via manipulating the OAuth state.

Mattermost versions 10.11.x <= 10.11.1, 10.10.x <= 10.10.2, 10.5.x <= 10.5.10 fail to verify a user has permission to join a Mattermost team using the original invite token which allows any attacked to join any team on a Mattermost server regardless of restrictions via manipulating the RelayState

Mattermost versions 10.7.x <= 10.7.0, 10.6.x <= 10.6.2, 10.5.x <= 10.5.3, 9.11.x <= 9.11.12 fails to properly invalidate personal access tokens upon user deactivation, allowing deactivated users to maintain full system access by exploiting access token validation flaws via continued usage of previously issued tokens.

Mattermost versions 10.7.x <= 10.7.0, 10.6.x <= 10.6.2, 10.5.x <= 10.5.3, 9.11.x <= 9.11.12 fail to clear Google OAuth credentials when converting user accounts to bot accounts, allowing attackers to gain unauthorized access to bot accounts via the Google OAuth signup flow.