Authenticated User SMTP Relay Abuse in OpenCATS

Executive Summary

OpenCATS before 0.10.0 has a missing authorization vulnerability in ajax/testEmailSettings.php. Any authenticated user, including those with read-level access, can send emails through the configured SMTP relay by providing testEmailAddress and fromAddress parameters. This allows sending a test message to any recipient with a spoofed From address.

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Detection Guidance

To detect this vulnerability, check if your OpenCATS instance is running a version before 0.10.0. Inspect the file ajax/testEmailSettings.php for the presence of the testEmailAddress and fromAddress parameters without proper authorization checks. Look for unauthorized email sending attempts in server logs.

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Impact Analysis

An attacker could exploit this to send phishing emails or spam from your domain, potentially tricking recipients into disclosing sensitive information. It may also allow unauthorized email communication using your system's SMTP relay, leading to reputational damage or abuse of your domain.

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Compliance Impact

This vulnerability could lead to unauthorized data exposure or communication, violating GDPR's data protection principles or HIPAA's integrity and confidentiality requirements. Organizations may face compliance penalties if this flaw enables data breaches or unauthorized access to sensitive information.

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Mitigation Strategies

Immediately upgrade OpenCATS to version 0.10.0 or later to address the missing authorization checks. Review and restrict access to AJAX endpoints, particularly ajax/testEmailSettings.php. Ensure proper user permission validation is enforced across all endpoints.

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