CVE-2019-19966 in Linux
Summary
by MITRE
In the Linux kernel before 5.1.6, there is a use-after-free in cpia2_exit() in drivers/media/usb/cpia2/cpia2_v4l.c that will cause denial of service, aka CID-dea37a972655.
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Analysis
by VulDB Data Team • 08/17/2025
The vulnerability identified as CVE-2019-19966 represents a critical use-after-free condition within the Linux kernel's cpia2 driver subsystem, affecting versions prior to 5.1.6. This flaw exists in the cpia2_exit() function located at drivers/media/usb/cpia2/cpia2_v4l.c, where improper memory management leads to a scenario where freed memory is accessed after deallocation. The cpia2 driver is responsible for supporting camera hardware in the Linux kernel, specifically handling USB camera devices through the cpia2 (Camera Port Interface Architecture 2) protocol. The vulnerability arises from a race condition or improper synchronization mechanism during device removal or driver cleanup operations, where memory allocated for camera device structures is freed but subsequent code paths still attempt to reference the freed memory locations.
This use-after-free condition falls under CWE-416, which specifically addresses the use of memory after it has been freed, making it a direct implementation of the classic memory safety vulnerability pattern. The operational impact of this vulnerability manifests as a denial of service condition, where the kernel experiences a crash or system instability when the cpia2_exit() function is invoked during driver cleanup or device removal. The system may become unresponsive or require a reboot to recover from the memory corruption caused by the improper access to freed memory. This vulnerability can be exploited by malicious actors who have access to the system to trigger the device removal sequence, potentially leading to persistent denial of service attacks against critical systems relying on USB camera functionality.
The exploitation of this vulnerability requires an attacker to have the ability to interact with USB camera devices or trigger the cpia2 driver cleanup process, which could occur during normal system operation or through crafted device removal sequences. The ATT&CK framework categorizes this as a system service disruption technique under the T1499 category, specifically targeting operating system security features through kernel-level memory corruption. The vulnerability demonstrates a fundamental flaw in kernel memory management practices, where proper synchronization and memory lifecycle management are not adequately enforced during driver cleanup operations. This type of vulnerability represents a significant risk to embedded systems, servers, and devices that rely on USB camera support, as it can be triggered through legitimate device operations and may not require elevated privileges to exploit.
The recommended mitigation strategy involves upgrading to Linux kernel version 5.1.6 or later, where the memory management issues in the cpia2 driver have been addressed through proper memory lifecycle handling and synchronization mechanisms. System administrators should prioritize patching affected systems, particularly those running embedded devices or server environments that may utilize USB camera hardware. Additionally, implementing proper access controls and monitoring for USB device interactions can help detect potential exploitation attempts. The fix typically involves ensuring that all references to allocated memory are properly nullified after deallocation and that proper synchronization primitives are used during driver cleanup operations to prevent race conditions that could lead to the use-after-free scenario. Organizations should also consider implementing kernel module whitelisting and monitoring to prevent unauthorized modification or loading of vulnerable drivers.