CVE-2007-4174 in Tor
Summary
by MITRE
Tor before 0.1.2.16, when ControlPort is enabled, does not properly restrict commands to localhost port 9051, which allows remote attackers to modify the torrc configuration file, compromise anonymity, and have other unspecified impact via HTTP POST data containing commands without valid authentication, as demonstrated by an HTML form (1) hosted on a web site or (2) injected by a Tor exit node.
If you want to get the best quality for vulnerability data then you always have to consider VulDB.
Analysis
by VulDB Data Team • 07/30/2019
The vulnerability described in CVE-2007-4174 represents a critical security flaw in the Tor anonymity network that existed in versions prior to 0.1.2.16. This issue specifically affects systems where the ControlPort functionality is enabled, creating a significant vector for remote exploitation that undermines the fundamental security guarantees that Tor is designed to provide. The flaw stems from inadequate access controls that permit remote attackers to interact with the Tor control interface without proper authentication mechanisms, fundamentally compromising the anonymity infrastructure that users rely upon for privacy protection.
The technical implementation of this vulnerability involves the ControlPort feature in Tor, which serves as a communication interface allowing external programs to control Tor's operation and configuration. When this port operates without proper localhost restrictions, it becomes accessible from remote network locations, enabling attackers to send HTTP POST requests containing malicious commands directly to the control interface. This configuration flaw allows unauthorized individuals to manipulate the torrc configuration file through simple web-based attacks, potentially altering core network parameters that affect routing behavior, exit node selection, and overall anonymity characteristics.
The operational impact of this vulnerability extends far beyond simple configuration modification, as demonstrated by the attack vectors mentioned in the CVE description. Attackers can host malicious HTML forms on websites that automatically submit commands to the vulnerable ControlPort, or they can inject malicious content through compromised Tor exit nodes that relay traffic between the attacker and the target system. This dual attack methodology significantly broadens the exploitation surface, as it can leverage both web-based delivery mechanisms and the inherent trust relationships within the Tor network itself. The compromise of the torrc file can lead to complete loss of anonymity for users, as attackers can modify routing parameters to create predictable traffic patterns or redirect connections through compromised nodes.
The security implications of this vulnerability align with multiple CWE categories including CWE-284 for improper access control and CWE-94 for code injection, as the flaw enables remote code execution through configuration manipulation. From an ATT&CK framework perspective, this vulnerability maps to techniques such as T1071.004 for application layer protocol usage and T1566 for phishing with malicious attachments, as attackers can exploit the web-based delivery mechanism to compromise Tor instances. The vulnerability also represents a significant threat to the integrity of the Tor network, as compromised nodes could be used to create coordinated attacks against other users or to gather intelligence about network topology and user behavior patterns.
Mitigation strategies for this vulnerability require immediate implementation of proper access controls and network segmentation to restrict ControlPort access to localhost only. System administrators must ensure that Tor instances are configured to bind the ControlPort exclusively to the local interface, preventing remote connections from external networks. Additionally, network-level firewalls should be configured to block external access to the ControlPort, and regular security audits should verify that Tor configurations maintain proper access restrictions. The patch for this vulnerability in Tor version 0.1.2.16 specifically addressed the control port access restrictions, requiring explicit configuration to enable remote access, thereby preventing the default insecure behavior that enabled this exploitation vector. Organizations using Tor should also implement monitoring for unauthorized configuration changes and maintain up-to-date security practices to prevent similar vulnerabilities from emerging in their deployments.