CVE-2024-23972

Executive Summary

CVE-2024-23972 is a critical buffer overflow vulnerability in the Sony XAV-AX5500 in-car entertainment system. The flaw resides in the USB host driver, where a specially crafted USB configuration descriptor can overflow a fixed-length buffer. This allows a physically present attacker to execute arbitrary code on the device without authentication. The vulnerability has a CVSS score of 6.8 (Medium), but the physical access requirement and potential for full device compromise elevate its risk in targeted scenarios. No public exploit code or patch is currently available.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
• Base Score: 6.8 (Medium)
• Attack Vector (AV): Physical (P) – The attacker must have physical access to the USB port.
• Attack Complexity (AC): Low (L) – No special conditions required.
• Privileges Required (PR): None (N) – No authentication needed.
• User Interaction (UI): None (N) – No user action required.
• Scope (S): Unchanged (U) – The vulnerability affects only the device.
• Confidentiality (C): High (H) – Full device data access.
• Integrity (I): High (H) – Full control over device operations.
• Availability (A): High (H) – Potential for denial of service or full compromise.

Threat Level: High for physical access scenarios. The lack of authentication and low complexity make it a prime target for USB-based attacks (e.g., "USB drop" attacks).

Deep Dive & Mechanics

The vulnerability is a classic stack-based buffer overflow (CWE-121) in the USB host driver of the Sony XAV-AX5500. When a USB device is connected, the driver parses the USB configuration descriptor. A malicious USB device can provide a descriptor with a bLength field that exceeds the expected size, causing the driver to copy data into a fixed-length buffer without proper bounds checking. This overwrites adjacent memory, including the return address on the stack, allowing an attacker to redirect execution to arbitrary code.

Key Technical Details:

• Trigger: A crafted USB configuration descriptor with an oversized bLength field.
• Buffer Location: Stack-based buffer in the USB host driver.
• Exploitation: Overwrite return address to jump to attacker-controlled shellcode.
• Impact: Full remote code execution on the device, potentially affecting vehicle systems.

Vulnerable vs. Patched Code

No patched code is available. The vulnerable code is in the USB host driver's descriptor parsing routine. A hypothetical fix would involve:

• Adding bounds checking on the bLength field before copying.
• Using safe string functions (e.g., strncpy instead of strcpy).
• Implementing stack canaries.

Vulnerable Code (Hypothetical):

void parse_usb_descriptor(char *descriptor) {
    char buffer[64];
    // No bounds check
    strcpy(buffer, descriptor);
}

Patched Code (Hypothetical):

void parse_usb_descriptor(char *descriptor, size_t len) {
    char buffer[64];
    if (len > sizeof(buffer) - 1) {
        // Handle error
        return;
    }
    strncpy(buffer, descriptor, len);
    buffer[len] = '\0';
}

Exploitation & Lab Setup

Red Team

Prerequisites:

• A Sony XAV-AX5500 device.
• A programmable USB device (e.g., Facedancer, USB Rubber Ducky, or custom firmware on a microcontroller).
• Knowledge of the device's memory layout (requires reverse engineering).

Exploitation Steps:

1. Reverse Engineer the USB Driver: Use a disassembler (e.g., Ghidra) to find the vulnerable function and calculate the offset to the return address.
2. Craft the USB Configuration Descriptor: Create a descriptor with an oversized bLength field containing shellcode and a return address overwrite.
3. Deliver the Payload: Connect the malicious USB device to the XAV-AX5500.
4. Trigger the Overflow: The driver parses the descriptor, overwrites the stack, and executes the shellcode.

Example Payload Structure (Hypothetical):

[Padding] [Return Address] [Shellcode]

• Padding: Fill buffer to reach return address.
• Return Address: Address of shellcode in memory.
• Shellcode: ARM or x86 code (depending on device architecture) to execute commands.

Blue Team

Detection:

• Monitor USB device enumeration logs for anomalous descriptors.
• Use USB traffic analysis tools (e.g., Wireshark with USBPcap) to inspect configuration descriptors.
• Implement endpoint detection and response (EDR) on the device if possible.

Prevention:

• Disable USB ports on the device if not needed.
• Use USB port blockers or physical access controls.
• Apply firmware updates as soon as available.

Indicators of Compromise (IOCs)

• USB Device Descriptor: A configuration descriptor with bLength > 64 bytes.
• Device Behavior: Unexpected reboots, crashes, or execution of unknown processes.
• Network Traffic: Outbound connections from the device to unknown IPs (if shellcode enables network access).
• File System Changes: New files or modified binaries in the device's storage.

Example IOC (YARA Rule):

rule CVE_2024_23972_USB_Descriptor {
    meta:
        description = "Detects oversized USB configuration descriptors"
        author = "Valters IT"
        date = "2024-01-01"
    strings:
        $descriptor = { 09 02 ?? ?? ?? ?? 01 00 00 }
    condition:
        $descriptor and #descriptor > 64
}

Detection Engineering

YARA Rule

rule CVE_2024_23972_USB_Overflow {
    meta:
        description = "Detects malicious USB configuration descriptors for CVE-2024-23972"
        author = "Valters IT"
        date = "2024-01-01"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2024-23972"
    strings:
        $usb_desc = { 09 02 [2-4] 01 00 00 }
        $large_len = { 09 02 [2-4] 01 00 00 }  // Simplified
    condition:
        $usb_desc and #usb_desc > 64
}

Sigma Rule

title: CVE-2024-23972 USB Configuration Descriptor Overflow
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects oversized USB configuration descriptors on Sony XAV-AX5500
author: Valters IT
date: 2024/01/01
logsource:
    product: windows
    service: usb
detection:
    selection:
        EventID: 2100  # USB device event
        Description|contains: "Configuration Descriptor"
        Length|>64
    condition: selection
falsepositives:
    - Legitimate USB devices with large descriptors (rare)
level: high

Suricata Rule

alert usb any any -> any any (msg:"CVE-2024-23972 USB Configuration Descriptor Overflow"; content:"|09 02|"; offset:0; depth:2; byte_test:1,>,64,2; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable USB Ports: If the USB feature is not required, disable it via the device settings.
2. Physical Security: Restrict physical access to the device (e.g., lock the vehicle).
3. Monitor for Updates: Check Sony's support page for firmware updates.

Long-Term Fix:

• Sony must release a firmware update that implements proper bounds checking in the USB driver.
• Apply the update as soon as it becomes available.

Workarounds:

• Use a USB port blocker that only allows charging, not data transfer.
• Implement a USB whitelist on the device (if supported).

Valters IT
DevSecOps & Cyber Threat Intelligence Expert