Executive Summary

This vulnerability exists in Mattermost Plugins versions up to 1.1.5, where the software fails to properly sanitize filenames received from federated peers before using them to create export destination paths.

Because of this, an administrator of a remote federated Mattermost server can exploit this flaw by sending a malicious filename through the shared-channel attachment sync protocol.

This allows the attacker to write files to arbitrary locations within the target server's filestore.

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Impact Analysis

The vulnerability can have severe impacts because it allows an attacker with administrative access on a federated Mattermost server to write files anywhere within the target server's filestore.

This can lead to complete compromise of the target system's confidentiality, integrity, and availability.

• Confidentiality impact: The attacker can potentially overwrite or add files, exposing sensitive data.
• Integrity impact: The attacker can modify or replace files, potentially injecting malicious code or corrupting data.
• Availability impact: The attacker could disrupt normal operations by overwriting critical files.

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Compliance Impact

The provided information does not specify how this vulnerability impacts compliance with common standards and regulations such as GDPR or HIPAA.

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Mitigation Strategies

To mitigate this vulnerability, you should upgrade Mattermost Plugins to a version later than 1.1.5 where the filename sanitization issue has been fixed.

Since the vulnerability allows an administrator of a remote federated Mattermost server to write files to arbitrary locations, limiting or disabling federation with untrusted servers until the update is applied can reduce risk.

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