Security researchers have disclosed a newly found vulnerability in Mattermost's Playbooks plugin. The vulnerability, assigned the identifier CVE-2024-47401, impacts Mattermost versions 9.10.x <= 9.10.2, 9.11.x <= 9.11.1, and 9.5.x <= 9.5.9. This vulnerability allows an attacker to exploit Playbooks by sending a large request which generates an amplified GraphQL response. As a result, it could potentially lead to a Denial of Service (DoS) attack which crashes the application.

In this long-read post, we will cover details of the vulnerability, provide code snippets to understand the issue, and present links to original references. We will ensure our discussion is in simple, easy-to-understand terms as we explore this critical Mattermost security issue.

Exploit Details

Mattermost uses Playbooks as a collaborative method for teams to manage incidents and other operational workflows that require coordination. The vulnerability in question exists due to the plugin failing to prevent detailed error messages from being displayed. The error messages are generated in response to a specially crafted request sent by an attacker.

When an attacker sends a large request that generates a detailed error message, it can cause an amplified GraphQL response. This amplified response, in turn, could result in a DoS attack that crashes the Mattermost application, effectively disabling users and teams from accessing it.

Let's consider the following code snippet to better understand the issue at hand

query {
  errors: allErrors {
    messages {
      ...ErrorFields
    }
  }
}

fragment ErrorFields on Error {
  code
  field
  message
}

An attacker can alter the above GraphQL query to include nested error fragments which would cause the server to generate an excessively large response.

PoC and Exploit Code

A Proof of Concept (PoC) demonstrating the exploit can be found on the original Github repository through this link. The exploit code details how an attacker can craft requests that generate large GraphQL responses, leading to the application's crash. Use the provided steps and examples to validate the vulnerability on the affected Mattermost versions.

Mitigation and Patch

Upon discovering the vulnerability, Mattermost developers have released patches for the affected versions. Users and organizations running Mattermost instances are required to update their installations. The full patch details and instructions can be found on the official Mattermost Changelog page for each affected version. The patches address the issue by limiting the error information disclosed in Playbooks responses, thus reducing the chances of amplifying GraphQL responses.

Conclusion

CVE-2024-47401 is a critical security vulnerability in Mattermost's Playbooks plugin that could lead to denial of service attacks in specific versions of the application. To mitigate this vulnerability, users and organizations are urged to apply the necessary patches as soon as possible. The provided code snippets, repository links, and mitigation steps should provide a solid understanding and course of action to address this issue.

Timeline

Published on: 10/29/2024 09:15:07 UTC
Last modified on: 10/29/2024 14:34:04 UTC