CVE-2016-3136 in Linux
Summary
by MITRE
The mct_u232_msr_to_state function in drivers/usb/serial/mct_u232.c in the Linux kernel before 4.5.1 allows physically proximate attackers to cause a denial of service (NULL pointer dereference and system crash) via a crafted USB device without two interrupt-in endpoint descriptors.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 10/07/2024
The vulnerability described in CVE-2016-3136 represents a critical denial of service flaw within the Linux kernel's USB serial driver subsystem. This issue affects the mct_u232_msr_to_state function in the drivers/usb/serial/mct_u232.c file, which handles communication with specific USB-to-serial converter devices. The vulnerability manifests when a maliciously crafted USB device is connected to a system running an affected kernel version, specifically before 4.5.1. The flaw is particularly concerning because it can be exploited by attackers who are physically proximate to the target system, making it a significant threat in environments where untrusted USB devices might be connected.
The technical root cause of this vulnerability lies in the improper handling of USB device descriptors within the mct_u232 driver. When a USB device is connected that lacks the required two interrupt-in endpoint descriptors, the kernel's USB serial subsystem fails to properly validate the device configuration before attempting to process its status information. The mct_u232_msr_to_state function assumes that these descriptors exist and attempts to dereference pointers to them without proper validation, leading to a NULL pointer dereference condition. This type of error falls under CWE-476 which specifically addresses NULL pointer dereference vulnerabilities, and represents a classic case of inadequate input validation in kernel space code where device-specific assumptions are made without proper verification.
The operational impact of this vulnerability is severe and can result in complete system crashes or denial of service conditions that require manual intervention to recover. When the NULL pointer dereference occurs, the kernel experiences a page fault that typically results in a system panic or crash, effectively rendering the affected system unusable until it is rebooted. This makes the vulnerability particularly dangerous in mission-critical systems or environments where uptime is essential. The attack vector requires only physical proximity to the target system, making it difficult to prevent through network-based security measures alone. According to ATT&CK framework, this vulnerability maps to T1211 - Exploitation for Defense Evasion and T1059 - Command and Scripting Interpreter, as it enables attackers to disrupt system operations and potentially use the resulting crash as a stepping stone for more complex attacks.
Mitigation strategies for CVE-2016-3136 involve immediate kernel updates to version 4.5.1 or later where the vulnerability has been patched. The fix implemented by the Linux kernel team addresses the core issue by adding proper validation checks for the presence of required USB endpoint descriptors before attempting to access them. Organizations should also implement additional security measures such as disabling USB device auto-loading for untrusted devices, implementing USB device whitelisting policies, and monitoring for unusual USB device connections. The vulnerability highlights the importance of proper input validation in kernel space drivers and serves as a reminder of the security implications of USB device handling in operating systems. System administrators should prioritize patching this vulnerability across all systems that may be exposed to untrusted USB devices, particularly in environments where physical security cannot be guaranteed.