CVE-2007-4702 in Mac OS X
Summary
by MITRE
The Application Firewall in Apple Mac OS X 10.5, when "Block all incoming connections" is enabled, does not prevent root processes or mDNSResponder from accepting connections, which might allow remote attackers or local root processes to bypass intended access restrictions.
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Analysis
by VulDB Data Team • 03/16/2021
The vulnerability described in CVE-2007-4702 represents a critical flaw in the implementation of network access controls within Apple Mac OS X 10.5 operating system. This issue specifically affects the Application Firewall component that is designed to protect systems from unauthorized network connections. When users configure the firewall to "Block all incoming connections," they expect a comprehensive network isolation that prevents any external entities from establishing connections to services running on their Mac systems. However, this security feature contains a significant bypass mechanism that undermines its intended protective function.
The technical flaw stems from the improper implementation of access control policies within the firewall subsystem. The Application Firewall in Mac OS X 10.5 fails to properly enforce connection blocking restrictions for certain privileged processes that operate with root privileges. Specifically, the mDNSResponder process, which handles multicast dns services essential for network discovery and local service announcement, continues to accept incoming connections even when the firewall is configured to block all incoming traffic. Additionally, root processes that require network access for legitimate system operations are also exempted from the firewall restrictions, creating a persistent backdoor that attackers can exploit to bypass network access controls.
This vulnerability creates substantial operational impact for Mac OS X 10.5 systems, particularly in environments where network security is paramount. The flaw allows remote attackers to establish connections to services that should be blocked, potentially enabling them to access system resources, perform reconnaissance activities, or launch further attacks. Local root processes can also exploit this bypass to maintain persistence or escalate privileges, making the vulnerability particularly dangerous in multi-user environments or systems where privilege escalation attacks are a concern. The security implications extend beyond simple network access bypass, as this flaw demonstrates a fundamental weakness in how privileged processes are handled within the firewall enforcement mechanism.
The vulnerability aligns with CWE-693, which addresses protection mechanism failures, and represents a specific instance of inadequate access control implementation where the firewall's protection mechanism fails to properly enforce security policies. From an attacker's perspective, this flaw maps to ATT&CK technique T1068, which involves exploiting privileges to gain system access. The issue also relates to CWE-284, which deals with improper access control, and demonstrates how access control mechanisms can be circumvented through improper privilege handling. Organizations using Mac OS X 10.5 should implement immediate mitigations including updating to newer versions of the operating system, disabling unnecessary services, and implementing additional network segmentation measures. System administrators should also consider disabling the mDNSResponder service if it is not required, and ensure that all network services are properly configured with appropriate access controls. The recommended approach involves a comprehensive security review of all system services and ensuring that privilege escalation paths are properly restricted to prevent unauthorized access to network resources.