CVE-2019-19533 in Linux
Summary
by MITRE
In the Linux kernel before 5.3.4, there is an info-leak bug that can be caused by a malicious USB device in the drivers/media/usb/ttusb-dec/ttusb_dec.c driver, aka CID-a10feaf8c464.
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Analysis
by VulDB Data Team • 03/07/2024
The vulnerability identified as CVE-2019-19533 represents a critical information disclosure flaw within the Linux kernel ecosystem affecting versions prior to 5.3.4. This security weakness specifically resides within the ttusb_dec.c driver file located in the drivers/media/usb/ttusb-dec/ directory of the kernel source tree. The vulnerability manifests when a maliciously crafted USB device connects to a system running an affected kernel version, creating a potential attack vector that could compromise system security and confidentiality.
The technical implementation of this information leak occurs through improper handling of data structures within the USB device driver code. When a USB device attempts to communicate with the system through the ttusb_dec driver, the kernel fails to properly validate or sanitize input data from the device, resulting in the exposure of sensitive kernel memory contents to user-space applications. This memory disclosure can reveal kernel addresses, internal data structures, or other confidential information that could aid attackers in developing more sophisticated exploitation techniques. The vulnerability is classified under CWE-200 as an exposure of sensitive information and aligns with ATT&CK technique T1059.001 for command and scripting interpreter execution.
The operational impact of this vulnerability extends beyond simple information disclosure, as it provides attackers with valuable insights into the kernel memory layout and internal state. This information can be leveraged to bypass security mechanisms such as kernel address space layout randomization kASLR, making subsequent exploitation attempts more successful. An attacker with physical access to a vulnerable system could potentially connect a malicious USB device to extract kernel memory contents, which could then be analyzed to identify potential weaknesses in the kernel's memory management or to develop more advanced exploits targeting other components of the system.
Mitigation strategies for CVE-2019-19533 primarily focus on kernel version updates to 5.3.4 or later, where the vulnerability has been patched through proper input validation and memory handling procedures. System administrators should prioritize updating their kernel versions, particularly in environments where physical USB port access cannot be restricted. Additional protective measures include implementing USB device whitelisting policies, disabling unnecessary USB drivers, and employing kernel lockdown mechanisms that prevent unauthorized access to kernel memory. The patch for this vulnerability specifically addresses the improper memory access patterns in the ttusb_dec driver, ensuring that all input data from USB devices is properly validated before being processed, thereby eliminating the information leak condition that previously existed in the kernel's USB subsystem.