CVE-2020-14457: Mattermost Server Sensitive Data Exposure
Summary
CVE-2020-14457: Mattermost Server Sensitive Data Exposure. Affects github.com/mattermost/mattermost-server/v5 versions < 5.20.0. Fixed in 5.20.0. How to fix ↓
Also tracked for
- github.com/mattermost/mattermost · Go
- mattermost · Bitnami
The same CVE-2020-14457 is tracked separately for each ecosystem and vendor. Its fix information is the same; the package and affected versions differ.
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Background
Mattermost Server is an open-source messaging platform that enables teams to collaborate and communicate securely. It is written in Go and provides various features such as real-time messaging, file sharing, and integrations with other tools. However, an issue has been discovered in Mattermost Server before version 5.20.0 that exposes sensitive data. This vulnerability, identified as CVE-2020-14457, allows non-members to receive broadcasted team details via the update_team WebSocket event.
Vulnerability Detail
The vulnerability arises from a flaw in the Mattermost Server code that fails to properly restrict access to team details. As a result, non-members who are connected to the WebSocket can receive sensitive information about the team. This could include confidential discussions, files, or other data shared within the team. The impact of this vulnerability is considered moderate, with a CVSS score of 5.3. It is important to note that this vulnerability has been addressed in version 5.20.0 of Mattermost Server.
How To Fix
Latest published version: v5.39.3 as of 23 Oct 2026
go get github.com/mattermost/mattermost-server/v5@v5.39.3Upgrading to it may include breaking changes; the version below is the minimum fixed release for this vulnerability.
If you need the minimum change
5.20.0
This is the first release that contains the fix.
go get github.com/mattermost/mattermost-server/v5@v5.20.0Tip — Not sure which version your app runs? Vulert can match this fix to it. Scan free →
Conclusion
The vulnerability in Mattermost Server (CVE-2020-14457) exposes sensitive team details to non-members. To mitigate this issue, it is crucial to upgrade to version 5.20.0 or later. This update includes the necessary fixes to restrict access to team information and prevent data exposure. For further support and assistance in vulnerability remediation, please contact DevNack.com.
See every vulnerability recorded for github.com/mattermost/mattermost-server/v5 →
FAQ
Mattermost Server is an open-source messaging platform that enables teams to collaborate and communicate securely. It provides features such as real-time messaging, file sharing, and integrations with other tools.
The vulnerability allows non-members to receive broadcasted team details, potentially exposing sensitive information shared within the team.
To fix this vulnerability, it is recommended to upgrade to Mattermost Server version 5.20.0 or later.
No, there is no known workaround for this vulnerability. Upgrading to the latest version is the recommended solution.
The vulnerability is considered moderate, with a CVSS score of 5.3. While it does expose sensitive data, it requires non-members to be connected to the WebSocket to exploit the issue.
Related vulnerabilities
Recent vulnerabilities recorded for github.com/mattermost/mattermost-server/v5.
