CVE-2016-4701 in macOS
Summary
by MITRE
Application Firewall in Apple OS X before 10.12 allows local users to cause a denial of service via vectors involving a crafted SO_EXECPATH environment variable.
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 09/20/2022
The vulnerability identified as CVE-2016-4701 resides within the Application Firewall component of Apple's macOS operating system, specifically affecting versions prior to 10.12. This flaw represents a significant security weakness that demonstrates the potential for local privilege escalation and system disruption through carefully crafted environmental parameters. The issue manifests when the system processes a maliciously constructed SO_EXECPATH environment variable, which triggers unexpected behavior in the firewall's processing mechanisms.
The technical implementation of this vulnerability exploits a flaw in how the Application Firewall handles certain environment variables during network service initialization. When a local user supplies a crafted SO_EXECPATH value, the system's firewall component fails to properly validate or sanitize this input before processing it within the network stack. This improper input handling creates a condition where the firewall's internal state becomes corrupted or enters an unstable processing loop, ultimately leading to system instability. The vulnerability specifically targets the socket execution path handling mechanism, which is fundamental to how network services are launched and managed within the macOS environment.
From an operational perspective, this vulnerability presents a serious risk to system availability and stability, as it allows any local user to trigger a denial of service condition that can render the Application Firewall ineffective. The impact extends beyond simple service disruption since the firewall protection mechanism may become completely non-functional, leaving the system exposed to network-based attacks. This represents a critical weakness in macOS security architecture, as local privilege escalation can result in complete system compromise. The vulnerability's classification aligns with CWE-170, which addresses improper input handling and the potential for malformed data to cause system instability, and it maps to ATT&CK technique T1068, which covers local privilege escalation through process manipulation.
The exploitation of this vulnerability requires minimal privileges since it targets local user capabilities, making it particularly concerning for multi-user systems where users may not have administrative access but can still disrupt system operations. Security professionals should note that this vulnerability demonstrates the importance of robust input validation in system-level components, especially those that handle network processing and security functions. The flaw underscores the necessity of implementing proper environment variable sanitization and input validation in all system services that interact with network stack components. Organizations should prioritize immediate patching of affected systems to address this vulnerability and should implement monitoring for unusual network behavior that might indicate exploitation attempts. The vulnerability also highlights the need for comprehensive security testing of system-level components, particularly those that handle environmental inputs during service initialization processes.
This vulnerability serves as a reminder of the critical importance of maintaining up-to-date operating system versions, as the issue was resolved in macOS 10.12 and subsequent releases. The flaw exemplifies how seemingly minor input handling issues can result in significant system instability and security implications. Security teams should conduct thorough assessments of their macOS environments to identify and remediate similar vulnerabilities that may exist in other system components or third-party applications that could be exploited in similar ways.