CVE-2018-21257

An issue was discovered in Mattermost Server before 5.1. It allows attackers to bypass intended access restrictions for setting a channel header via the Channel header slash command API...

CVE-2015-9548

An issue was discovered in Mattermost Server before 1.2.0. It allows attackers to cause a denial of service memory consumption via a small compressed file that has a large size when uncompressed...

CVE-2017-18921

An issue was discovered in Mattermost Server before 3.6.0 and 3.5.2. XSS can occur via a link on an error page...

CVE-2017-18908

An issue was discovered in Mattermost Server before 4.0.0, 3.10.2, and 3.9.2. A password-reset request was sometime sent to an attacker-provided e-mail address...

CVE-2017-18884

An issue was discovered in Mattermost Server before 4.3.0, 4.2.1, and 4.1.2. It allows attackers to gain privileges by using a registered OAuth application with personal access tokens...

CVE-2017-18894

An issue was discovered in Mattermost Server before 4.2.0, 4.1.1, and 4.0.5, when used as an OAuth 2.0 service provider. Sometimes. resource-owner authorization is bypassed, allowing account takeover...

CVE-2016-11083

An issue was discovered in Mattermost Server before 2.2.0. It allows XSS because it configures files to be opened in a browser window...

CVE-2016-11076

An issue was discovered in Mattermost Server before 3.0.0. It does not ensure that a cookie is used over SSL...

CVE-2016-11067

An issue was discovered in Mattermost Server before 3.2.0. It allowed crafted posts that could cause a web browser to hang...

CVE-2016-11075

An issue was discovered in Mattermost Server before 3.0.0. It allows attackers to obtain sensitive information about team URLs via an API...

Mattermost Server 9.11.x < 9.11.12 / 10.4.x < 10.4.5 / 10.5.x < 10.5.3 / 10.6.x < 10.6.2 (MMSA-2025-00459)

The version of Mattermost Server installed on the remote host is prior to 9.11.12, 10.4.5, 10.5.3, or 10.6.2. It is, therefore, affected by a vulnerability as referenced in the MMSA-2025-00459 advisory. - 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...

Mattermost Server 9.11.x < 9.11.12 / 10.5.x < 10.5.3 Multiple Vulnerabilities (MMSA-2025-00455, MMSA-2025-00456)

The version of Mattermost Server installed on the remote host is prior to 9.11.12 or 10.5.3. It is, therefore, affected by multiple vulnerabilities as referenced in the MMSA-2025-0045500456 advisory. - Mattermost versions 10.5.x = 10.5.2, 9.11.x = 9.11.11 failed to properly verify a user's...

Incorrect Authorization

Overview Affected versions of this package are vulnerable to Incorrect Authorization due to the improper verification of user permissions when accessing groups. An attacker can view unauthorized group information by crafting a malicious API request. Remediation Upgrade...

Incorrect Authorization

Overview Affected versions of this package are vulnerable to Incorrect Authorization due to the improper verification of user permissions when accessing groups. An attacker can view unauthorized group information by crafting a malicious API request. Remediation Upgrade...

Incorrect Authorization

Overview github.com/mattermost/mattermost/server/channels/app is a private-cloud Slack alternative Affected versions of this package are vulnerable to Incorrect Authorization due to the improper verification of user permissions when accessing groups. An attacker can view unauthorized group...

Denial Of Service (DoS)

github.com/mattermost/mattermost-server is vulnerable to Denial Of Service DoS. The vulnerability is due to insufficient input validation caused by a failure to properly validate user-controlled props in the RetrospectivePost custom post type of the Playbooks plugin, which allows an attacker to...

Denial Of Service (DoS)

github.com/mattermost/mattermost-server is vulnerable to Denial Of Service DoS. The vulnerability is due to missing validation of uniqueness and quantity of task actions in the UpdateRunTaskActions GraphQL operation, allowing attackers to overload the server by submitting excessive actions...

Improper Authorization

github.com/mattermost/mattermost-server is vulnerable to improper authorization. The vulnerability is due to insufficient permission validation for the API endpoint /plugins/playbooks/api/v0/signal/keywords/ignore-thread, allowing any user or attacker to delete posts created by the Playbooks bot...

Timing Attack

github.com/mattermost/mattermost-server is vulnerable to a Timing attack. The vulnerability is due to improper implementation of constant time comparison when comparing the MSTeams plugin webhook secret, allows an attacker to exploit timing differences in the comparison process to extract the...

Improper Access Control

github.com/mattermost/mattermost-server is vulnerable to improper access control. The vulnerability is due to insufficient enforcement of MFA checks due to a failure to verify that the requesting user matches the target user ID when modifying MFA settings, allowing privilege escalation...