CVE-2025-54400

Executive Summary

CVE-2025-54400 is a critical stack-based buffer overflow vulnerability in the formPingCmd functionality of the Planet WGR-500 router, firmware version v1.3411b190912. The vulnerability resides in the counts request parameter, which is used to construct the command string "ping -c <counts> <ipaddr> 2>&1 > %s &". An unauthenticated attacker can send a series of specially crafted HTTP requests to trigger a stack-based buffer overflow, leading to remote code execution (RCE) with root privileges. The CVSS score is 8.8 (High), and no patch is currently available. This vulnerability is particularly dangerous due to the lack of authentication required and the potential for full device compromise.

Supply Chain & Package Security

This vulnerability is not related to NPM, PyPI, Go, or Ruby packages. It is a firmware-level issue in an embedded network device (Planet WGR-500 router). Supply chain risks include the distribution of unpatched firmware images and the potential for malicious actors to exploit this vulnerability in IoT botnets or targeted attacks.

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)

The threat level is Critical due to the ease of exploitation (no authentication, low complexity) and the high impact on confidentiality, integrity, and availability. The EPSS score is 0.0%, indicating low exploitation likelihood at the time of analysis, but this may change as proof-of-concept code emerges.

Deep Dive & Mechanics

The vulnerability is a classic stack-based buffer overflow in the formPingCmd function. The function constructs a system command string using user-supplied parameters counts and ipaddr. The counts parameter is directly concatenated into the command without proper bounds checking:

ping -c <counts> <ipaddr> 2>&1 > %s &

An attacker can send an HTTP POST request to the vulnerable endpoint with an overly long counts value. This overwrites the stack buffer, allowing control of the return address and subsequent execution of arbitrary code. The vulnerability is triggered by sending a series of HTTP requests, likely to bypass any rate limiting or to fill a buffer before overflow.

The device runs a web server that exposes the formPingCmd functionality, typically used for network diagnostics. No authentication is required to access this endpoint, making it exploitable from the local network or potentially from the WAN if the management interface is exposed.

Vulnerable vs. Patched Code

Vulnerable Code (Conceptual):

void formPingCmd(char *counts, char *ipaddr) {
    char cmd[256];
    snprintf(cmd, sizeof(cmd), "ping -c %s %s 2>&1 > /tmp/ping_result &", counts, ipaddr);
    system(cmd);
}

The snprintf function is used, but the buffer size is insufficient for large counts values, leading to overflow.

Patched Code (Hypothetical):

void formPingCmd(char *counts, char *ipaddr) {
    char cmd[256];
    // Validate input length and content
    if (strlen(counts) > 10 || !is_numeric(counts)) {
        return error;
    }
    snprintf(cmd, sizeof(cmd), "ping -c %s %s 2>&1 > /tmp/ping_result &", counts, ipaddr);
    system(cmd);
}

A proper patch would include input validation (e.g., limiting counts to numeric values and a maximum length) and using safer functions like snprintf with proper size checks.

Exploitation & Lab Setup

Red Team

Lab Setup:

1. Obtain a Planet WGR-500 router with firmware v1.3411b190912.
2. Connect to the device's LAN interface and obtain its IP address (e.g., 192.168.1.1).
3. Use a tool like curl or a custom Python script to send HTTP requests.

Exploitation Steps:

1. Identify the vulnerable endpoint (likely /goform/formPingCmd).
2. Craft a payload for the counts parameter that overflows the buffer and overwrites the return address with a controlled value.
3. Use a ROP chain or shellcode to execute arbitrary commands (e.g., reverse shell).
4. Send the malicious HTTP request:

   curl -X POST http://192.168.1.1/goform/formPingCmd \
     -d "counts=$(python -c 'print("A"*256 + "\x90"*16 + shellcode)')&ipaddr=127.0.0.1"
   

5. The device executes the payload, granting a root shell.

Note: No public exploit code is available, so this is a conceptual approach.

Blue Team

Detection:

• Monitor for HTTP requests to /goform/formPingCmd with abnormally long counts parameters.
• Use network intrusion detection systems (NIDS) to flag requests with counts values exceeding 10 characters.
• Analyze logs for unusual system commands or processes spawned by the web server.

Hunting:

• Search for ping -c commands in system logs that have excessively long arguments.
• Look for unexpected outbound connections from the device (e.g., reverse shells).

Indicators of Compromise (IOCs)

• Network IOCs:

  • HTTP POST requests to /goform/formPingCmd with counts parameter > 20 characters.
  • Outbound connections from the device to unusual IP addresses on high ports (e.g., 4444, 1337).
  • DNS queries to known C2 domains.

• Host IOCs:

  • Presence of unexpected files in /tmp/ (e.g., /tmp/ping_result with unusual content).
  • Modified system binaries or scripts.
  • Unusual processes running as root (e.g., /bin/sh spawned by the web server).

• File IOCs:

  • Hash of malicious payloads (e.g., shellcode) – to be determined upon exploit release.

Detection Engineering

YARA Rule

rule CVE_2025_54400_Planet_WGR500_Overflow {
    meta:
        description = "Detects exploit attempts for CVE-2025-54400 in HTTP requests"
        author = "Valters IT"
        date = "2025-01-01"
        reference = "CVE-2025-54400"
    strings:
        $http_post = "POST /goform/formPingCmd" ascii
        $counts_param = "counts=" ascii
        $long_count = /counts=[A-Za-z0-9]{20,}/ ascii
    condition:
        $http_post and $counts_param and $long_count
}

Sigma Rule

title: CVE-2025-54400 Exploit Attempt
id: 12345678-1234-1234-1234-123456789abc
status: experimental
description: Detects HTTP requests targeting the formPingCmd endpoint with long counts parameter
author: Valters IT
date: 2025-01-01
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        cs-uri-stem: '/goform/formPingCmd'
        cs-uri-query|contains: 'counts='
    condition: selection and |len(cs-uri-query) > 100
falsepositives:
    - Legitimate network diagnostics with long IP addresses
level: high

Suricata Rule

alert http any any -> $HOME_NET any (msg:"CVE-2025-54400 Planet WGR-500 Buffer Overflow Attempt"; flow:to_server; content:"POST"; http_method; content:"/goform/formPingCmd"; http_uri; content:"counts="; http_client_body; pcre:"/counts=[A-Za-z0-9]{20,}/Ri"; classtype:attempted-admin; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Isolate affected devices: Disconnect Planet WGR-500 routers from untrusted networks (especially the WAN).
2. Disable remote management: If not required, disable the web management interface on the WAN side.
3. Monitor for exploitation: Use the provided detection rules to identify potential attacks.

Long-term Fix:

• Vendor patch: Contact Planet support for a firmware update. If no patch is available, consider replacing the device.
• Input validation: Implement a WAF (Web Application Firewall) rule to block requests with overly long counts parameters.
• Network segmentation: Place affected devices in a separate VLAN with strict access controls.

Workaround:

• If the device cannot be replaced, manually modify the firmware (if possible) to add input validation, or use a reverse proxy to filter malicious requests.

Valters IT
Securing Digital Frontiers