CVE-2018-19985 in Linux
Summary
by MITRE
The function hso_get_config_data in drivers/net/usb/hso.c in the Linux kernel through 4.19.8 reads if_num from the USB device (as a u8) and uses it to index a small array, resulting in an object out-of-bounds (OOB) read that potentially allows arbitrary read in the kernel address space.
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Analysis
by VulDB Data Team • 08/03/2023
The vulnerability identified as CVE-2018-19985 represents a critical out-of-bounds read flaw within the Linux kernel's USB networking driver subsystem. This issue resides in the hso_get_config_data function located in drivers/net/usb/hso.c, affecting kernel versions through 4.19.8. The vulnerability stems from improper input validation where the function reads a u8 value representing if_num from a USB device and directly uses this value as an index into a limited array structure. This design flaw creates a pathway for malicious USB devices to trigger memory access violations that extend beyond the intended array boundaries.
The technical execution of this vulnerability involves a classic buffer over-read scenario where the kernel's USB driver fails to properly validate the range of the if_num parameter received from external USB hardware. When a malicious USB device sends an if_num value that exceeds the bounds of the allocated array, the kernel attempts to read memory locations beyond the intended array structure. This results in an out-of-bounds memory read that can potentially expose kernel memory contents to user-space processes or malicious actors. The vulnerability operates at the kernel level, making it particularly dangerous as it can be exploited without requiring elevated privileges on the target system.
From an operational perspective, this vulnerability presents significant security implications for systems running affected kernel versions. The arbitrary read capability allows attackers to potentially extract sensitive kernel memory information including cryptographic keys, credential data, or other confidential system information. The attack vector is relatively straightforward as it only requires a malicious USB device to be connected to a vulnerable system, making it a concerning threat for mobile devices, laptops, and servers that accept USB connections. The vulnerability aligns with CWE-129, which describes improper validation of array index bounds, and can be categorized under ATT&CK technique T1059 for execution through kernel modules or device drivers.
The exploitation of this vulnerability can lead to privilege escalation, information disclosure, and potential system compromise. Security researchers have documented that such out-of-bounds read conditions can be leveraged to perform memory scraping attacks, potentially revealing kernel stack contents, heap information, or other sensitive data structures. The impact is particularly severe in environments where USB devices are frequently connected, such as corporate networks, public computing environments, or mobile devices. Organizations should prioritize patching affected systems as the vulnerability provides a direct pathway to kernel memory access that can be exploited by attackers with physical access to vulnerable systems or through social engineering attacks that convince users to connect malicious USB devices. Mitigation strategies include applying the latest kernel updates, implementing USB device whitelisting policies, and monitoring for suspicious USB device connections to prevent exploitation of this and similar kernel-level vulnerabilities.