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Total
77
Critical
1
High
9
Medium
49
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0
Mattermost Plugins versions <=2.1.3.0 fail to limit the request body size on the {{/changes}} webhook endpoint which allows an authenticated attacker to cause memory exhaustion and denial of service via sending an oversized JSON payload. Mattermost Advisory ID: MMSA-2026-00611
Mattermost versions 9.11.X <= 9.11.1, 9.5.x <= 9.5.9 icorrectly issues two sessions when using desktop SSO - one in the browser and one in desktop with incorrect settings.
Mattermost versions 9.9.x <= 9.9.1, 9.5.x <= 9.5.7, 9.10.x <= 9.10.0 and 9.8.x <= 9.8.2 fail to restrict which roles can promote a user as system admin which allows a System Role with edit access to the permissions section of system console to update their role (e.g. member) to include the `manage_system` permission, effectively becoming a System Admin.
Mattermost versions 9.5.x <= 9.5.7, 9.10.x <= 9.10.0 fail to enforce proper access controls which allows any authenticated user, including guests, to mark any channel inside any team as read for any user.
Mattermost versions 9.9.x <= 9.9.1, 9.5.x <= 9.5.7, 9.10.x <= 9.10.0, 9.8.x <= 9.8.2 fail to restrict the input in POST /api/v4/users which allows a user to manipulate the creation date in POST /api/v4/users tricking the admin into believing their account is much older.
Mattermost versions 9.9.x <= 9.9.1, 9.5.x <= 9.5.7, 9.10.x <= 9.10.0, 9.8.x <= 9.8.2 fail to sanitize user inputs in the frontend that are used for redirection which allows for a one-click client-side path traversal that is leading to CSRF in User Management page of the system console.
Mattermost versions 9.9.x <= 9.9.1, 9.5.x <= 9.5.7, 9.10.x <= 9.10.0 and 9.8.x <= 9.8.2 fail to ensure that remote/synthetic users cannot create sessions or reset passwords, which allows the munged email addresses, created by shared channels, to be used to receive email notifications and to reset passwords, when they are valid, functional emails.
Mattermost versions 9.5.x <= 9.5.7 and 9.10.x <= 9.10.0 fail to time limit and size limit the CA path file in the ElasticSearch configuration which allows a System Role with access to the Elasticsearch system console to add any file as a CA path field, such as /dev/zero and, after testing the connection, cause the application to crash.
Mattermost versions 9.9.x <= 9.9.1, 9.5.x <= 9.5.7, 9.10.x <= 9.10.0, 9.8.x <= 9.8.2, when shared channels are enabled, fail to redact remote users' original email addresses stored in user props when email addresses are otherwise configured not to be visible in the local server."
Mattermost versions 9.9.x <= 9.9.0, 9.5.x <= 9.5.6, 9.7.x <= 9.7.5, 9.8.x <= 9.8.1 fail to properly safeguard an error handling which allows a malicious remote to permanently delete local data by abusing dangerous error handling, when share channels were enabled.
Mattermost versions 9.9.x <= 9.9.0, 9.5.x <= 9.5.6, 9.7.x <= 9.7.5 and 9.8.x <= 9.8.1 fail to disallow unsolicited invites to expose access to local channels, when shared channels are enabled, which allows a malicious remote to send an invite with the ID of an existing local channel, and that local channel will then become shared without the consent of the local admin.
Mattermost versions 9.9.x <= 9.9.0, 9.5.x <= 9.5.6, 9.7.x <= 9.7.5 and 9.8.x <= 9.8.1 fail to properly validate that the channel that comes from the sync message is a shared channel, when shared channels are enabled, which allows a malicious remote to add users to arbitrary teams and channels
Mattermost versions 9.9.x <= 9.9.0, 9.5.x <= 9.5.6, 9.7.x <= 9.7.5, 9.8.x <= 9.8.1 fail to disallow the modification of local users when syncing users in shared channels. which allows a malicious remote to overwrite an existing local user.
Mattermost versions 9.9.x <= 9.9.0, 9.5.x <= 9.5.6 fail to properly validate synced reactions, when shared channels are enabled, which allows a malicious remote to create arbitrary reactions on arbitrary posts
Mattermost versions 9.8.0, 9.7.x <= 9.7.4, 9.6.x <= 9.6.2, 9.5.x <= 9.5.5 fail to prevent specifying a RemoteId when creating a new user which allows an attacker to specify both a remoteId and the user ID, resulting in creating a user with a user-defined user ID. This can cause some broken functionality in User Management such administrative actions against the user not working.
Mattermost versions 9.8.x <= 9.8.0, 9.7.x <= 9.7.4, 9.6.x <= 9.6.2 and 9.5.x <= 9.5.5, when shared channels are enabled, fail to use constant time comparison for remote cluster tokens which allows an attacker to retrieve the remote cluster token via a timing attack during remote cluster token comparison.
Mattermost versions 9.5.x <= 9.5.5 and 9.8.0 fail to properly sanitize the recipients of a webhook event which allows an attacker monitoring webhook events to retrieve the channel IDs of archived or restored channels.
Mattermost versions 9.8.0, 9.7.x <= 9.7.4, 9.6.x <= 9.6.2 and 9.5.x <= 9.5.5 fail to prevent users from specifying a RemoteId for their posts which allows an attacker to specify both a remoteId and the post ID, resulting in creating a post with a user-defined post ID. This can cause some broken functionality in the channel or thread with user-defined posts
Mattermost versions 9.5.x <= 9.5.5 and 9.8.0 fail to sanitize the RemoteClusterFrame payloads before audit logging them which allows a high privileged attacker with access to the audit logs to read message contents.
Mattermost versions 9.5.x <= 9.5.5 and 9.8.0, when using shared channels with multiple remote servers connected, fail to check that the remote server A requesting the server B to update the profile picture of a user is the remote that actually has the user as a local one . This allows a malicious remote A to change the profile images of users that belong to another remote server C that is connected to the server A.
Mattermost version 2.10.0 and earlier fails to sanitize deeplink paths, which allows an attacker to perform CSRF attacks against the server.
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.
Mattermost fails to limit the log size of server logs allowing an attacker sending specially crafted requests to different endpoints to potentially overflow the log.
Mattermost fails to limit the amount of data extracted from compressed archives during board import in Mattermost Boards allowing an attacker to consume excessive resources, possibly leading to Denial of Service, by importing a board using a specially crafted zip (zip bomb).
Mattermost fails to properly check a redirect URL parameter allowing for an open redirect was possible when the user clicked "Back to Mattermost" after providing a invalid custom url scheme in /oauth/{service}/mobile_login?redirect_to=
Mattermost fails to properly validate the "Show Full Name" option in a few endpoints in Mattermost Boards, allowing a member to get the full name of another user even if the Show Full Name option was disabled.
Mattermost fails to check whether the “Allow users to view archived channels” setting is enabled during permalink previews display, allowing members to view permalink previews of archived channels even if the “Allow users to view archived channels” setting is disabled.
Mattermost fails to properly limit the characters allowed in different fields of a block in Mattermost Boards allowing a attacker to consume excessive resources, possibly leading to Denial of Service, by patching the field of a block using a specially crafted string.
Mattermost fails to use innerText / textContent when setting the channel name in the webapp during autocomplete, allowing an attacker to inject HTML to a victim's page by create a channel name that is valid HTML. No XSS is possible though.
Mattermost fails to check if hardened mode is enabled when overriding the username and/or the icon when posting a post. If settings allowed integrations to override the username and profile picture when posting, a member could also override the username and icon when making a post even if the Hardened Mode setting was enabled
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.
Mattermost fails to properly sanitize the user object when updating the username, resulting in the password hash being included in the response body.
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
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 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
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.
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
Mattermost fails to properly validate permissions when demoting and deactivating a user allowing for a system/user manager to demote / deactivate another manager
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.
Mattermost fails to properly verify the permissions when managing/updating a bot allowing a User Manager role with user edit permissions to manage/update bots.
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 before performing different actions to public playbooks, resulting a guest being able 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 be able to access and download the attachment of a deleted message
Mattermost iOS app fails to properly validate the server certificate while initializing the TLS connection allowing a network attacker to intercept the WebSockets connection.
Mattermost fails to unescape Markdown strings in a memory-efficient way, allowing an attacker to cause a Denial of Service by sending a message containing a large number of escaped characters.
Mattermost fails to sanitize code permalinks, allowing an attacker to preview code from private repositories by posting a specially crafted permalink on a channel.
Mattermost fails to validate links on external websites when constructing a preview for a linked website, allowing an attacker to cause a denial-of-service by a linking to a specially crafted webpage in a message.
Mattermost fails to sanitize ephemeral error messages, allowing an attacker to obtain arbitrary message contents by a specially crafted /groupmsg command.
Mattermost fails to properly truncate the postgres error log message of a search query failure allowing an attacker to cause the creation of large log files which can result in Denial of Service
When creating a playbook run via the /dialog API, Mattermost fails to validate all parameters, allowing an authenticated attacker to edit an arbitrary channel post.
Mattermost fails to check if an admin user account active after an oauth2 flow is started, allowing an attacker with admin privileges to retain persistent access to Mattermost by obtaining an oauth2 access token while the attacker's account is deactivated.
Mattermost fails to check channel membership when accessing message threads, allowing an attacker to access arbitrary posts by using the message threads API.
Mattermost fails to properly check the permissions when executing commands allowing a member with no permissions to post a message in a channel to actually post it by executing channel commands.
Mattermost fails to verify if the requestor is a sysadmin or not, before allowing `install` requests to the Apps allowing a regular user send install requests to the Apps.
Mattermost Apps Framework fails to verify that a secret provided in the incoming webhook request allowing an attacker to modify the contents of the post sent by the Apps.
Mattermost fails to normalize UTF confusable characters when determining if a preview should be generated for a hyperlink, allowing an attacker to trigger link preview on a disallowed domain using a specially crafted link.
Mattermost Sever fails to redact the DB username and password before emitting an application log during server initialization.
Mattermost fails to invalidate existing authorization codes when deauthorizing an OAuth2 app, allowing an attacker possessing an authorization code to generate an access token.
Mattermost fails to check the "Show Full Name" setting when rendering the result for the /plugins/focalboard/api/v2/users API call, allowing an attacker to learn the full name of a board owner.
A missing permissions check in Mattermost Playbooks in Mattermost allows an attacker to modify a playbook via the /plugins/playbooks/api/v0/playbooks/[playbookID] API.
A missing permissions check in the /plugins/playbooks/api/v0/runs API in Mattermost allows an attacker to list and view playbooks belonging to a team they are not a member of.
A denial-of-service vulnerability in the Mattermost allows an authenticated user to crash the server via multiple requests to one of the API endpoints which could fetch a large amount of data.
A denial-of-service vulnerability in Mattermost allows an authenticated user to crash the server via multiple large autoresponder messages.
A denial-of-service vulnerability in the Mattermost Playbooks plugin allows an authenticated user to crash the server via multiple large requests to one of the Playbooks API endpoints.
The Guest account feature in Mattermost version 6.7.0 and earlier fails to properly restrict the permissions, which allows a guest user to fetch a list of all public channels in the team, in spite of not being part of those channels.
The legacy Slack import feature in Mattermost version 6.7.0 and earlier fails to properly limit the sizes of imported files, which allows an authenticated attacker to crash the server by importing large files via the Slack import REST API.
One of the API in Mattermost version 6.3.0 and earlier fails to properly protect the permissions, which allows the system administrators to combine the two distinct privileges/capabilities in a way that allows them to override certain restricted configurations like EnableUploads.
Mattermost 6.3.0 and earlier fails to properly sanitize the HTML content in the email invitation sent to guest users, which allows registered users with special permissions to invite guest users to inject unescaped HTML content in the email invitations.
Mattermost 6.3.0 and earlier fails to protect email addresses of the creator of the team via one of the APIs, which allows authenticated team members to access this information resulting in sensitive & private information disclosure.
Mattermost 6.2 and earlier fails to sufficiently process a specifically crafted GIF file when it is uploaded while drafting a post, which allows authenticated users to cause resource exhaustion while processing the file, resulting in server-side Denial of Service.
Mattermost 6.1 and earlier fails to sufficiently validate permissions while viewing archived channels, which allows authenticated users to view contents of archived channels even when this is denied by system administrators by directly accessing the APIs.
Mattermost 6.0.2 and earlier fails to sufficiently sanitize user's password in audit logs when user creation fails.
Mattermost 5.38 and earlier fails to sufficiently sanitize clipboard contents, which allows a user-assisted attacker to inject arbitrary web script in product deployments that explicitly disable the default CSP.
Fixed a bypass for a reflected cross-site scripting vulnerability affecting OAuth-enabled instances of Mattermost.
An issue was discovered in Mattermost Mobile Apps before 1.31.2 on iOS. Unintended third-party servers could sometimes obtain authorization tokens, aka MMSA-2020-0022.
An issue was discovered in Mattermost Mobile Apps before 1.26.0. An attacker can use directory traversal with the Video Preview feature to overwrite arbitrary files on a device.