Denial of service in mattermost mobile apps and server via emoji reactions

Mattermost fails to check if a custom emoji reaction exists when sending it to a post and to limit the amount of custom emojis allowed to be added in a post, allowing an attacker sending a huge amount of non-existent custom emojis in a post to crash the mobile app of a user seeing the post and to crash the server due to overloading when clients attempt to retrive the aforementioned post. 

Mattermost version 2.10.0 and earlier fails to sanitize deeplink paths, which allows an attacker to perform CSRF attacks against the server.

Mattermost version 8.1.6 and earlier fails to sanitize channel mention data in posts, which allows an attacker to inject markup in the web client.

Client side path traversal due to lack of route parameters validation

Mattermost webapp fails to validate route parameters in/<TEAM_NAME>/channels/<CHANNEL_NAME> allowing an attacker to perform a client-side path traversal.

Insecure Direct Object Reference in /plugins/focalboard/ api/v2/users of Mattermost Boards

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.

Denial of Service via Link Preview in /api/v4/redirect_location

Mattermost fails to properly sanitize the request to /api/v4/redirect_location allowing an attacker, sending a specially crafted request to /api/v4/redirect_location, to fill up the memory due to caching large items.

Password hash in response body after username update

Mattermost fails to properly sanitize the user object when updating the username, resulting in the password hash being included in the response body. 

Denial of Service via crashing the Calls Plugin

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

Regex DoS from a malicious server enrolled in Desktop

Mattermost fails to properly validate a RegExp built off the server URL path, allowing an attacker in control of an enrolled server to mount a Denial Of Service.

Lack of Hardening against media exploitation from a remote origin

Mattermost Desktop fails to correctly handle permissions or prompt the user for consent on certain sensitive ones allowing media exploitation from a malicious mattermost server

Mobile app freezes when receiving a post with hundreds of emojis

Mattermost Mobile fails to limit the maximum number of Markdown elements in a post allowing an attacker to send a post with hundreds of emojis to a channel and freeze the mobile app of users when viewing that particular channel. 

Mattermost Desktop logs all keystrokes during initial run after fresh installation 

Mattermost Desktop fails to set an appropriate log level during initial run after fresh installation resulting in logging all keystrokes including password entry being logged. 

Denial of Service via multiple identical User IDs in /api/v4/users/ids

Mattermost fails to deduplicate input IDs allowing a simple user to cause the application to consume excessive resources and possibly crash by sending a specially crafted request to /api/v4/users/ids with multiple identical IDs.

File Information Leak via IDOR in file_id in Draft Posts

Mattermost fails to properly check the creator of an attached file when adding the file to a draft post, potentially exposing unauthorized file information.

Denial of Service via Opengraph Data Cache

Mattermost fails to enforce a limit for the size of the cache entry for OpenGraph data allowing an attacker to send a specially crafted request to the /api/v4/opengraph filling the cache and turning the server unavailable.

DoS via Channel Notification Properties

Mattermost fails to enforce character limits in all possible notification props allowing an attacker to send a really long value for a notification_prop resulting in the server consuming an abnormal quantity of computing resources and possibly becoming temporarily unavailable for its users.

A team member can soft delete other teams that they are not part of

Mattermost fails to properly validate the permissions when soft deleting a team allowing a team member to soft delete other teams that they are not part of

A system/user manager can demote / deactivate another manager

Mattermost fails to properly validate permissions when demoting and deactivating a user allowing for a system/user manager to demote / deactivate another manager

System Role with manage posts permission can read posts of Direct Messages

Mattermost fails to properly check permissions when retrieving a post allowing for a System Role with the permission to manage channels to read the posts of a DM conversation.

Full name disclosure via team top membership with Show Full Name option disabled

Mattermost fails to check the Show Full Name option at the /api/v4/teams/TEAM_ID/top/team_members endpoint allowing a member to get the full name of another user even if the Show Full Name option was disabled