CVE-2017-16536 in Linux
Summary
by MITRE
The cx231xx_usb_probe function in drivers/media/usb/cx231xx/cx231xx-cards.c in the Linux kernel through 4.13.11 allows local users to cause a denial of service (NULL pointer dereference and system crash) or possibly have unspecified other impact via crafted system calls.
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Analysis
by VulDB Data Team • 01/06/2023
The CVE-2017-16536 vulnerability resides within the Linux kernel's cx231xx USB driver subsystem, specifically in the cx231xx_usb_probe function located at drivers/media/usb/cx231xx/cx231xx-cards.c. This flaw represents a critical security issue that affects Linux kernel versions through 4.13.11, where local attackers can exploit a NULL pointer dereference condition to compromise system stability. The vulnerability manifests when crafted system calls are executed against the affected kernel module, creating a scenario where the driver fails to properly validate input parameters before attempting to access memory locations.
The technical implementation of this vulnerability stems from inadequate input validation within the cx231xx_usb_probe function, which is responsible for initializing USB capture devices in the Linux kernel. When a malicious user or process invokes specific system calls that trigger this function, the code path fails to properly check for NULL pointer references before dereferencing pointers that may not have been initialized. This condition creates a classic null pointer dereference scenario where the kernel attempts to access memory at address zero or an invalid memory location, resulting in immediate system termination. The vulnerability operates at the kernel level, making it particularly dangerous as it can be exploited by any local user with access to system resources, without requiring special privileges or network connectivity.
The operational impact of CVE-2017-16536 extends beyond simple denial of service, as it can potentially lead to system crashes and complete system instability. When the NULL pointer dereference occurs, the kernel's memory management subsystem terminates the offending process and may cause the entire system to crash, requiring manual reboot to restore normal operation. This type of vulnerability aligns with CWE-476 which identifies NULL Pointer Dereference as a common weakness in software systems. The attack surface is particularly concerning because the vulnerability exists within a widely used USB driver module that supports various capture devices including digital television tuners and video capture hardware, making it prevalent across multiple Linux distributions and embedded systems that utilize these devices.
From an adversarial perspective, this vulnerability maps to several ATT&CK techniques including privilege escalation and system compromise through kernel-level exploitation. The local nature of the attack means that any user with access to the system can potentially trigger the vulnerability, making it a significant concern for multi-user environments and server systems. The exploitation process involves crafting specific system calls that will invoke the vulnerable code path, which can be achieved through various programming interfaces such as ioctl commands that are typically used to communicate with kernel modules. This type of vulnerability demonstrates the critical importance of input validation and proper error handling in kernel space code, as even minor oversights in parameter validation can lead to complete system compromise.
Mitigation strategies for CVE-2017-16536 primarily involve applying kernel updates that contain the patched version of the cx231xx driver code. The fix typically includes adding proper NULL pointer checks before dereferencing any pointers within the probe function, ensuring that all input parameters are validated before being processed. System administrators should immediately apply the relevant kernel security patches from their distribution vendors, as the vulnerability affects a core kernel subsystem that is essential for proper system operation. Additionally, organizations should consider implementing kernel lockdown mechanisms and restricting access to kernel modules where possible, though this approach provides only partial protection against local exploitation. The vulnerability serves as a reminder of the critical importance of thorough code review and security testing for kernel-level components, particularly those that handle device initialization and hardware interaction scenarios.