Nextcloud Mail app (for Nextcloud, a self-hosted productivity platform) contains a critical vulnerability (CVE-2024-52508) that can expose sensitive account credentials to attackers under certain circumstances. Specifically, when a user is trying to set up a new account with an email address like user@example.tld that does not support auto-configuration, and an attacker managed to register autoconfig.tld, the used email details would be sent to the attacker's server.

This long-read post will explain the vulnerability in detail, demonstrate a code snippet to reproduce the issue, provide links to original references, and discuss the possible exploit scenarios. The recommendations for mitigating this vulnerability include upgrading Nextcloud Mail app to version 1.14.6, 1.15.4, 2.2.11, 3.6.3, 3.7.7, or 4...

Vulnerability Details

The vulnerability stems from the mail app's handling of custom auto-configuration domains, where the app sends the email account credentials to the auto-configuration server without validating the server's authenticity. This means that if an attacker has control of a custom auto-configuration domain mentioned above, they can capture the email credentials of unsuspecting users who are trying to set up their accounts.

Here's a simplified code snippet that demonstrates the issue

function getAutoconfigServer(emailDomain) {
  // ... code to resolve autoconfig server for emailDomain ...
  return "https://autoconfig."; + emailDomain + "/mail/config-v1.1.xml";
}

function setupMailAccount(email, password) {
  let emailDomain = getEmailDomain(email); // Extracts domain from email address
  let autoconfigServer = getAutoconfigServer(emailDomain);
  
  // The following line sends the credentials to the autoconfig server without
  // checking if the server is genuine.
  let response = fetch(autoconfigServer, {
    method: "POST",
    body: JSON.stringify({ email: email, password: password }),
  });
}

Exploit Scenarios

*Scenario 1:* The attacker registers a domain like autoconfig.tld and sets up a server to listen for incoming requests to capture email credentials.

*Scenario 2:* An attacker is already in control of such a domain and leverages this vulnerability to harvest email credentials sent from Nextcloud Mail app users who are trying to set up their accounts.

Mitigation and Remediation

To mitigate this vulnerability, it is crucial to upgrade the Nextcloud Mail app to version 1.14.6, 1.15.4, 2.2.11, 3.6.3, 3.7.7, or 4.., which contain patches that prevent leaking email credentials:

Update to a secure version of Nextcloud Mail app

# As the Nextcloud admin user:
occ app:update mail --version 1.14.6

or

occ app:update mail --version 1.15.4

2. Nextcloud Official Mail app Repository - https://github.com/nextcloud/mail
3. Nextcloud Mail App Release Notes and Changelog - https://github.com/nextcloud/mail/releases

Conclusion

The CVE-2024-52508 vulnerability in Nextcloud Mail app is a severe issue that allows attackers to capture sensitive email credentials from unsuspecting users. By upgrading the Nextcloud Mail app to a secure version (1.14.6, 1.15.4, 2.2.11, 3.6.3, 3.7.7, or 4..), administrators can protect their users and prevent credential leakage.

Timeline

Published on: 11/15/2024 18:15:29 UTC
Last modified on: 11/18/2024 17:11:56 UTC