CVE-2023-37453: Linux Kernel USB Subsystem DoS Vulnerability

CVE-2023-37453 Overview

CVE-2023-37453 is an out-of-bounds read vulnerability discovered in the USB subsystem of the Linux kernel through version 6.4.2. The flaw exists in the read_descriptors function within drivers/usb/core/sysfs.c, which can result in a system crash when processing malformed USB descriptor data. This vulnerability was identified through automated kernel fuzzing and represents a memory safety issue that could be exploited through physical access to a vulnerable system.

Critical Impact

An attacker with physical access to a vulnerable Linux system can trigger a kernel crash by connecting a specially crafted USB device, leading to denial of service conditions.

Affected Products

• Linux Kernel versions through 6.4.2
• Systems running affected kernel versions with USB subsystem enabled
• Embedded Linux devices with exposed USB interfaces

Discovery Timeline

• 2023-07-06 - CVE-2023-37453 published to NVD
• 2025-05-05 - Last updated in NVD database

Technical Details for CVE-2023-37453

Vulnerability Analysis

This vulnerability falls under CWE-125 (Out-of-Bounds Read), a memory corruption class where code reads data from a location outside the intended buffer boundaries. In the context of the Linux kernel USB subsystem, the read_descriptors function in drivers/usb/core/sysfs.c fails to properly validate buffer boundaries when processing USB device descriptors exposed through the sysfs interface.

When a user-space process reads USB descriptor information through the sysfs filesystem, the kernel must serialize and return descriptor data. The vulnerable code path does not adequately verify that read operations remain within the allocated buffer, allowing reads beyond the intended memory region. This can expose kernel memory contents or trigger a kernel panic when accessing invalid memory addresses.

The vulnerability requires physical access to the target system, meaning an attacker must be able to connect a malicious USB device or manipulate USB descriptor data through physical means. While this limits remote exploitation, it remains a significant concern for kiosk systems, publicly accessible workstations, and environments where physical security cannot be guaranteed.

Root Cause

The root cause of CVE-2023-37453 lies in insufficient bounds checking within the read_descriptors function. When USB descriptors are read through the sysfs interface, the function calculates offsets and sizes based on descriptor metadata. However, the validation logic fails to account for all edge cases where malformed or maliciously crafted descriptor data could specify sizes or offsets that exceed the actual buffer allocation.

The kernel commits addressing this issue implement proper boundary validation before performing read operations, ensuring that calculated offsets and sizes cannot exceed the allocated buffer dimensions. Multiple patches were required to comprehensively address different code paths where this boundary checking was insufficient.

Attack Vector

Exploitation of this vulnerability requires physical access to the target system. An attacker would need to:

1. Gain physical access to a USB port on the vulnerable system
2. Connect a specially crafted USB device that provides malformed descriptor data
3. Trigger the vulnerable code path through descriptor enumeration or sysfs access

When the kernel processes the malformed descriptors, the out-of-bounds read occurs, potentially causing:

• Kernel memory information disclosure
• System crash due to invalid memory access
• Denial of service through repeated exploitation

The vulnerability does not require authentication or user interaction beyond the physical connection of the malicious device. Systems with automated USB device handling are particularly susceptible, as they may automatically enumerate connected devices without user confirmation.

Detection Methods for CVE-2023-37453

Indicators of Compromise

• Unexpected kernel panics or system crashes coinciding with USB device connections
• Kernel oops messages referencing read_descriptors or drivers/usb/core/sysfs.c in stack traces
• Unusual USB device enumeration activity in system logs
• Repeated kernel crashes on systems with public USB access

Detection Strategies

• Monitor kernel logs for oops or panic messages containing references to USB sysfs operations
• Implement USB device whitelisting to prevent enumeration of unknown or untrusted devices
• Deploy endpoint detection solutions capable of identifying anomalous USB device behavior
• Configure kernel crash dump analysis to capture and analyze panic events for forensic investigation

Monitoring Recommendations

• Enable kernel logging for USB subsystem events using dmesg monitoring
• Configure system monitoring to alert on kernel panic events and unexpected reboots
• Review USB device connection logs regularly on systems with physical access exposure
• Implement SentinelOne endpoint protection for comprehensive kernel-level threat detection

How to Mitigate CVE-2023-37453

Immediate Actions Required

• Update the Linux kernel to a patched version that includes the security fixes
• Restrict physical access to USB ports on critical systems where feasible
• Implement USB device authorization policies to prevent automatic enumeration of unknown devices
• Monitor for kernel crash events that may indicate exploitation attempts

Patch Information

Multiple kernel commits have been released to address this vulnerability. The primary fixes are available in the Linux kernel git repository:

• Linux Kernel Commit 1e4c574
• Linux Kernel Commit 85d07c5
• Linux Kernel Commit de28e46
• Linux Kernel Commit ff33299

Organizations should apply these patches through their distribution's package management system or by updating to a kernel version that includes these fixes. Additional technical details and discussion are available on the Kernel Mailing List and the Syzkaller Bug Report.

Workarounds

• Disable USB device enumeration on systems where USB functionality is not required using kernel boot parameters
• Implement physical USB port blockers on kiosk or publicly accessible systems
• Configure USB authorization to require manual approval for new devices using usbguard or similar tools
• Restrict access to USB sysfs entries through appropriate file permissions where applicable

# Disable USB autosuspend and implement basic USB restrictions
echo "authorized_default=0" > /sys/bus/usb/devices/usb*/authorized_default

# Install and configure USBGuard for device whitelisting
apt install usbguard
systemctl enable usbguard
systemctl start usbguard