CVE-2012-3723 in Mac OS X
Summary
by MITRE
Apple Mac OS X before 10.7.5 does not properly handle the bNbrPorts field of a USB hub descriptor, which allows physically proximate attackers to execute arbitrary code or cause a denial of service (memory corruption and system crash) by attaching a USB device.
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Analysis
by VulDB Data Team • 01/09/2025
The vulnerability identified as CVE-2012-3723 represents a critical buffer overflow flaw in Apple Mac OS X operating systems prior to version 10.7.5. This security weakness resides within the USB hub descriptor handling mechanism, specifically in how the system processes the bNbrPorts field of USB hub descriptors. The issue stems from inadequate input validation and boundary checking when parsing USB device configuration data, creating a scenario where maliciously crafted USB devices can trigger unpredictable system behavior. The vulnerability's classification aligns with CWE-129, which addresses improper validation of length of input data, and CWE-787, concerning out-of-bounds write operations. Attackers exploiting this flaw need only physical proximity to the target system, making it particularly concerning for environments where untrusted USB devices might be connected.
The technical implementation of this vulnerability occurs during the USB device enumeration process when the operating system attempts to parse USB hub descriptors to determine the number of ports available on a USB hub. The bNbrPorts field in USB hub descriptors contains a single byte that specifies the number of downstream ports, but the Mac OS X kernel fails to properly validate this value against expected ranges. When an attacker crafts a USB device with an invalid bNbrPorts value that exceeds the allocated buffer space, the system's USB driver performs an unchecked write operation into kernel memory. This memory corruption can result in arbitrary code execution with kernel privileges or cause system crashes through memory corruption that destabilizes the operating system's kernel space. The flaw's exploitation requires minimal attack surface since it operates at the hardware interface level, making it particularly dangerous in environments where USB devices are frequently connected and disconnected.
The operational impact of CVE-2012-3723 extends beyond simple system instability to encompass potential full system compromise and data exposure risks. Attackers who successfully exploit this vulnerability can gain kernel-level privileges, enabling them to bypass system security controls, access sensitive system files, modify system configurations, and potentially establish persistent backdoors. The vulnerability's proximity requirement means it could be exploited in targeted attacks against specific individuals or organizations where physical access to computing devices is possible, such as in corporate environments, public spaces, or during travel. From an attacker's perspective, this vulnerability maps to ATT&CK technique T1059.007 for command execution and T1068 for local privilege escalation. The attack vector falls under the category of physical tampering with hardware, which is particularly concerning given that USB devices are commonly used for data transfer and system administration tasks.
Mitigation strategies for CVE-2012-3723 primarily focus on system updates and operational security measures. The most effective remediation involves upgrading to Apple Mac OS X version 10.7.5 or later, which includes patches that properly validate the bNbrPorts field and implement appropriate buffer bounds checking. Organizations should also implement USB device whitelisting policies, restrict USB device connectivity in sensitive environments, and deploy USB device monitoring solutions to detect anomalous USB activity. System administrators should consider disabling unnecessary USB ports, particularly those accessible to untrusted users, and implement USB device authentication mechanisms where possible. The vulnerability's exploitation requires minimal sophistication, making it a prime target for automated attack tools, thus emphasizing the importance of proactive patch management and network security monitoring. Additionally, security awareness training for users about the risks of connecting unknown USB devices can provide an additional layer of defense against social engineering aspects of this attack vector.