Mattermost vulnerabilities

Mattermost versions 11.5.x <= 11.5.1 and 10.11.x <= 10.11.13 fail to validate the Host header when constructing response URLs for custom slash commands. An authenticated attacker can redirect slash command responses to an attacker-controlled server via a spoofed Host header.

Mattermost versions 11.5.x <= 11.5.1 fail to verify channel membership when processing AI-assisted message rewrites. An authenticated attacker can read the content of threads in private channels and direct messages they do not have access to via a crafted request to the post rewrite endpoint.

Mattermost versions 11.5.x <= 11.5.1, 10.11.x <= 10.11.13 fail to check if {{team_id}} was being changed when updating playbooks, allowing users with only {{Manage Playbook Configurations}} permission to change a playbook's team, bypassing manage members restriction via PUT api.

Mattermost versions 11.5.x <= 11.5.1, 10.11.x <= 10.11.13, 11.4.x <= 11.4.3 fail to enforce slash command trigger-word uniqueness during command updates. An authenticated team member with Manage Own Slash Commands permission can hijack and impersonate existing system or custom slash commands by editing their own slash command trigger to an already-registered trigger via the command update API.

Mattermost versions 11.5.x <= 11.5.1, 10.11.x <= 10.11.13, 11.4.x <= 11.4.3 fail to validate 7zip archive structure before processing, allowing an authenticated attacker to cause server memory exhaustion and denial of service via uploading a specially crafted 7zip file with excessive folder declarations.

Mattermost versions 11.5.x <= 11.5.1, 10.11.x <= 10.11.13 fail to validate that the RefreshedToken differs from the original invite token during remote cluster invite confirmation, which allows an authenticated attacker to bypass token rotation and reuse the original invite token via sending a crafted invite confirmation with a RefreshedToken matching the original token.

Mattermost versions 11.5.x <= 11.5.1, 10.11.x <= 10.11.13, 11.4.x <= 11.4.3 fail to check the create_post channel permission during post edit operations. An authenticated attacker with revoked posting privileges can modify their existing posts via direct API requests to the post update and patch endpoints.

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 malicious code via injecting JS as part of those values.

Mattermost versions 11.5.x <= 11.5.1, 10.11.x <= 10.11.13, 11.4.x <= 11.4.3 fail to limit the size of the request body on the start meeting API endpoint, which allows an authenticated attacker to cause resource exhaustion or denial of service via a crafted oversized HTTP POST request to {{/api/v1/meetings}}.

Mattermost versions 11.5.x <= 11.5.1, 10.11.x <= 10.11.13, 11.4.x <= 11.4.3 fail to validate that a remote cluster has access to a channel before processing membership removal requests during shared channel membership sync. A malicious remote cluster can remove any user from any channel, including private channels, via crafted membership sync messages targeting channels the remote cluster is not authorized to access.

Mattermost versions 11.1.x <= 11.1.0, 11.0.x <= 11.0.5, 10.12.x <= 10.12.3, and 10.11.x <= 10.11.7 fail to verify that post actions invoking /share-issue-publicly were created by the Jira plugin. A malicious Mattermost user could exfiltrate Jira tickets when victim users interact with affected 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 fails to validate user channel membership when attaching Mattermost posts as comments to Jira issues, allowing 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 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. This 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 through 11.0.4, 10.12.x through 10.12.2, and 10.11.x through 10.11.6 fail to validate the UTF-8 format of the WebSocket request field, allowing an attacker to crash the Calls plugin by sending a malformed request.

Mattermost versions 10.11.x up to 10.11.4 fail to validate redirect URLs on the /error page. An attacker can 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 <= 1.10.0 fail to implement CSRF protection on the Calls widget page. An authenticated attacker can 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. This allows attackers to hijack the GitHub reaction feature to make users add reactions to arbitrary GitHub objects via crafted notification posts.

Mattermost versions 10.11.x <= 10.11.4 and 10.5.x <= 10.5.12 fail to validate user permissions when accessing files and subscribing to blocks in Boards. An authenticated user can access files from other boards and subscribe to blocks from boards they do not have access to.

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 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. Any authenticated user can view team email addresses via the GET /api/v4/channels/{channel_id}/common_teams endpoint.

Mattermost versions 10.11.x <= 10.11.3 and 10.5.x <= 10.5.11 fail to enforce access permissions on the Agents plugin, allowing 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, and 10.12.x <= 10.12.0 fail to sanitize user data, allowing 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 through 10.11.3, 10.5.x through 10.5.11, and 10.12.x through 10.12.0 fail to validate the relationship between the post being updated and the MSTeams plugin OAuth flow. This allows an attacker to edit arbitrary posts via a crafted MSTeams plugin OAuth redirect URL.

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

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

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

Mattermost versions 10.11.x <= 10.11.3 and 10.5.x <= 10.5.11 fail to properly validate team membership permissions in the Add Channel Member API. This allows users from one team to access user metadata and channel membership information from other teams via the API endpoint.

Mattermost versions 10.11.x <= 10.11.1, 10.10.x <= 10.10.2, and 10.5.x <= 10.5.10 fail to verify that a user has permission to join a Mattermost team using the original invite token. This allows an attacker to join any team on a Mattermost server regardless of restrictions by manipulating the RelayState parameter.

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 10.5.x <= 10.5.10 and 10.11.x <= 10.11.2 fail to use constant-time comparison for sensitive string comparisons, allowing 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 10.10.x <= 10.10.2, 10.5.x <= 10.5.10, 10.11.x <= 10.11.2 fail to validate email ownership during Slack import, allowing 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 and 10.11.x <= 10.11.2 fail to properly validate guest user permissions when adding channel members. This allows guest users to add any team members to their private channels via the /api/v4/channels/{channel_id}/members endpoint.

Mattermost versions 10.5.x <= 10.5.12 and 10.11.x <= 10.11.2 fail to properly validate guest user permissions when accessing channel information. This 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 <= 10.5.8 and 9.11.x <= 9.11.17 fail to properly validate access controls, allowing any authenticated user to download sensitive files via the board file download endpoint using UUID enumeration.

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 validate import directory path configuration, allowing admin users to execute arbitrary code via malicious plugin upload to the prepackaged plugins directory.

Mattermost versions 10.5.x <= 10.5.9 fail to properly validate redirect URLs, allowing attackers to redirect users to malicious sites via crafted OAuth login URLs.

Mattermost versions 10.10.x <= 10.10.1, 10.5.x <= 10.5.9, 10.9.x <= 10.9.4 fail to validate the redirect_to parameter, allowing an attacker to craft a malicious link that, after a user authenticates with SAML, could post the user's cookies to an attacker-controlled URL.

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, allowing authenticated users to access unauthorized posts and poison link previews via hash collision attacks on FNV-1 hashing.

Mattermost versions 10.10.x <= 10.10.1 fail to properly sanitize user data during shared channel membership synchronization. Malicious or compromised remote clusters can access sensitive user information via unsanitized user objects. The vulnerability affects Mattermost Server instances with shared channels enabled.

Mattermost fails to restrict which parameters' values it takes from the request during signup, allowing an attacker to register users as inactive. This blocks them from later accessing Mattermost without the system admin activating their accounts.

Mattermost fails to sanitize post metadata during audit logging, resulting in permalinks contents being logged.

Mattermost fails to properly validate the requesting user permissions when updating a system admin, allowing a user manager to update a system admin's details such as email, first name and last name.

Mattermost fails to check if the requesting user is a guest, allowing guests to view, join, edit, export, and archive public playbooks.

Mattermost fails to delete the attachments when deleting a message in a thread, allowing a simple user to still access and download the attachment of a deleted message.

Mattermost fails to properly validate a gif image file, allowing an attacker to consume a significant amount of server resources, making the server unresponsive for an extended period of time.

Mattermost fails to properly validate markdown, allowing an attacker to crash the server via a specially crafted markdown input.

Mattermost fails to invalidate previously generated password reset tokens when a new reset token is created.

Mattermost fails to properly show information in the UI, allowing a system admin to modify a board state. This allows any user with a valid sharing link to join the board with editor access, without the UI showing the updated permissions.

Mattermost fails to disable public Boards after the 'Enable Publicly-Shared Boards' configuration option is disabled, resulting in previously-shared public Boards to remain accessible.

Mattermost fails to properly check the authorization of POST /api/v4/teams when passing a team override scheme ID in the request. This allows an authenticated attacker with knowledge of a Team Override Scheme ID to create a new team with said team override scheme.