CVE-2019-19537 in Linux
Summary
by MITRE
In the Linux kernel before 5.2.10, there is a race condition bug that can be caused by a malicious USB device in the USB character device driver layer, aka CID-303911cfc5b9. This affects drivers/usb/core/file.c.
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Analysis
by VulDB Data Team • 03/07/2024
The vulnerability identified as CVE-2019-19537 represents a critical race condition flaw within the Linux kernel's USB character device driver layer, specifically affecting the drivers/usb/core/file.c component. This vulnerability emerges from the improper handling of concurrent access patterns during USB device operations, creating a window where malicious actors can exploit temporal inconsistencies in the kernel's USB subsystem. The issue manifests when a malicious USB device attempts to trigger specific sequences of operations that expose the race condition, potentially leading to arbitrary code execution or privilege escalation within the kernel space.
The technical root cause of this vulnerability lies in the improper synchronization mechanisms within the USB character device driver implementation. When multiple threads or processes attempt to access USB character device files simultaneously, the kernel fails to properly enforce mutual exclusion during critical sections of code execution. This race condition allows for a malicious USB device to manipulate the timing and sequence of operations to cause memory corruption or unexpected behavior in the kernel's USB subsystem. The vulnerability is classified under CWE-362, which specifically addresses race conditions in software systems where multiple threads or processes access shared resources without proper synchronization.
From an operational perspective, this vulnerability poses significant security risks to Linux systems that support USB character device drivers, particularly those running kernel versions prior to 5.2.10. Attackers can exploit this weakness by connecting a malicious USB device that triggers the race condition through carefully crafted USB communication sequences. The impact extends beyond simple privilege escalation as the vulnerability can potentially lead to complete system compromise, allowing attackers to execute arbitrary code with kernel-level privileges. This makes it particularly dangerous in environments where USB devices are frequently connected or where systems lack proper USB device access controls.
The exploitation of CVE-2019-19537 aligns with several tactics described in the MITRE ATT&CK framework, specifically targeting the privilege escalation and execution phases of an attack lifecycle. The vulnerability enables adversaries to move from user-level access to kernel-level privileges, which is a critical step in establishing persistent access to compromised systems. Additionally, this weakness can be leveraged as part of broader attack chains where the compromised system serves as a foothold for further lateral movement or data exfiltration activities. Organizations should note that the vulnerability's impact is amplified in environments where USB devices are frequently used for administrative tasks or where default USB device access policies are permissive.
Mitigation strategies for CVE-2019-19537 primarily focus on upgrading to Linux kernel versions 5.2.10 or later, where the race condition has been properly addressed through enhanced synchronization mechanisms. System administrators should also implement USB device access controls, including disabling unnecessary USB device drivers, restricting USB device access through kernel parameters, and implementing USB device whitelisting policies. Organizations should consider deploying kernel lockdown mechanisms and ensuring that USB device drivers are properly configured to prevent unauthorized access to kernel resources. The vulnerability serves as a reminder of the critical importance of maintaining up-to-date kernel versions and implementing comprehensive USB security policies in enterprise environments.