Improper Validation Of OAuth State Tokens

github.com/mattermost/mattermost-server is vulnerable to improper validation of OAuth state tokens. The vulnerability is due to insufficient validation during the OpenID Connect OAuth flow, which allows an attacker to manipulate authentication data and take over a user account under specific...

Improper Access Control

github.com/mattermost/mattermost-server is vulnerable to improper access control. The vulnerability is due to failure to validate user channel membership when attaching posts to Jira issues, which allows an authenticated attacker with Jira plugin access to read post content and attachments from...

Improper Authorization

github.com/mattermost/mattermost-server is vulnerable to improper authorization. The vulnerability is due to failure in validating the relationship between the post being updated and the MSTeams plugin OAuth flow, which allows an attacker to exploit this via a crafted OAuth redirect URL to edit...

Sensitive Information Exposure

github.com/mattermost/mattermost-server is vulnerable to sensitive information exposure. The vulnerability is due to improper sanitization of user data, which allows system administrators to access password hashes and MFA secrets via the POST /api/v4/users/userid/email/verify/member endpoint...

Improper Access Control

github.com/mattermost/mattermost-server is vulnerable to improper access control. The vulnerability is due to failure in enforcing the "Allow users to view archived channels" setting, which allows an attacker to access archived channel content and files via the "Open in Channel" functionality fro...

GO-2026-4916 Mattermost doesn't rate limit login requests, allowing DoS in github.com/mattermost/mattermost-server

Mattermost doesn't rate limit login requests, allowing DoS in github.com/mattermost/mattermost-server. NOTE: The source advisory for this report contains additional versions that could not be automatically mapped to standard Go module versions. If this is causing false-positive reports from...

PT-2026-29956

Mattermost doesn't rate limit login requests, allowing DoS in github.com/mattermost/mattermost-server. NOTE: The source advisory for this report contains additional versions that could not be automatically mapped to standard Go module versions. If this is causing false-positive reports from...

GO-2026-4726 Mattermost fails to limit the size of responses from integration action endpoints in github.com/mattermost/mattermost-server

Mattermost fails to limit the size of responses from integration action endpoints in github.com/mattermost/mattermost-server. NOTE: The source advisory for this report contains additional versions that could not be automatically mapped to standard Go module versions. If this is causing...

GO-2026-4725 Mattermost fails to properly validate User-Agent header tokens in github.com/mattermost/mattermost-server

Mattermost fails to properly validate User-Agent header tokens in github.com/mattermost/mattermost-server. NOTE: The source advisory for this report contains additional versions that could not be automatically mapped to standard Go module versions. If this is causing false-positive reports from...

Incorrect Implementation of Authentication Algorithm

Overview github.com/mattermost/mattermost-server is an open source Slack-alternative in Golang and React. Affected versions of this package are vulnerable to Incorrect Implementation of Authentication Algorithm in the IsSameUser function. An attacker can gain unauthorized access to arbitrary user...

GO-2026-4786 Mattermost fails to validate user's authentication method when processing account auth type switch in github.com/mattermost/mattermost-server

Mattermost fails to validate user's authentication method when processing account auth type switch in github.com/mattermost/mattermost-server. NOTE: The source advisory for this report contains additional versions that could not be automatically mapped to standard Go module versions. If this is...

GO-2026-4735 Mattermost fails to filter invite IDs based on user permissions in github.com/mattermost/mattermost-server

Mattermost fails to filter invite IDs based on user permissions in github.com/mattermost/mattermost-server. NOTE: The source advisory for this report contains additional versions that could not be automatically mapped to standard Go module versions. If this is causing false-positive reports from...

GO-2026-4729 Mattermost allows a removed team member to enumerate all public channels within a private team in github.com/mattermost/mattermost-server

Mattermost allows a removed team member to enumerate all public channels within a private team in github.com/mattermost/mattermost-server. NOTE: The source advisory for this report contains additional versions that could not be automatically mapped to standard Go module versions. If this is causi...

GO-2026-4727 Mattermost fails to bound memory allocation when processing PSD image files in github.com/mattermost/mattermost-server

Mattermost fails to bound memory allocation when processing PSD image files in github.com/mattermost/mattermost-server. NOTE: The source advisory for this report contains additional versions that could not be automatically mapped to standard Go module versions. If this is causing false-positive...

GO-2026-4734 Mattermost fails to preserve the redacted state of burn-on-read posts during deletion in github.com/mattermost/mattermost-server

Mattermost fails to preserve the redacted state of burn-on-read posts during deletion in github.com/mattermost/mattermost-server. NOTE: The source advisory for this report contains additional versions that could not be automatically mapped to standard Go module versions. If this is causing...

GO-2026-4749 Mattermost fails to validate team-specific upload_file permissions in github.com/mattermost/mattermost-server

Mattermost fails to validate team-specific uploadfile permissions in github.com/mattermost/mattermost-server. NOTE: The source advisory for this report contains additional versions that could not be automatically mapped to standard Go module versions. If this is causing false-positive reports fro...

GO-2026-4745 Mattermost fails to properly enforce read permissions in search API endpoints in github.com/mattermost/mattermost-server

Mattermost fails to properly enforce read permissions in search API endpoints in github.com/mattermost/mattermost-server. NOTE: The source advisory for this report contains additional versions that could not be automatically mapped to standard Go module versions. If this is causing false-positive...

GO-2026-4732 Mattermost allows attackers to spoof permalink embeds in github.com/mattermost/mattermost-server

Mattermost allows attackers to spoof permalink embeds in github.com/mattermost/mattermost-server. NOTE: The source advisory for this report contains additional versions that could not be automatically mapped to standard Go module versions. If this is causing false-positive reports from...

GO-2026-4733 Mattermost fails to bound memory allocation when processing DOC files in github.com/mattermost/mattermost-server

Mattermost fails to bound memory allocation when processing DOC files in github.com/mattermost/mattermost-server. NOTE: The source advisory for this report contains additional versions that could not be automatically mapped to standard Go module versions. If this is causing false-positive reports...

GO-2026-4746 Mattermost fails to canonicalize IPv4-mapped IPv6 addresses before reserved IP validation in github.com/mattermost/mattermost-server

Mattermost fails to canonicalize IPv4-mapped IPv6 addresses before reserved IP validation in github.com/mattermost/mattermost-server. NOTE: The source advisory for this report contains additional versions that could not be automatically mapped to standard Go module versions. If this is causing...