CVE-2024-39945

Executive Summary

CVE-2024-39945 is a high-severity vulnerability affecting Dahua products. The flaw allows an authenticated attacker (with administrator credentials) to send a specially crafted data packet to a vulnerable interface, causing the device to crash. This results in a denial of service (DoS) condition. The vulnerability has a CVSS score of 4.9 (Medium), but its impact is limited to availability. No public proof-of-concept (PoC) or exploit code is currently available. The vendor has not yet released a patch.

CVSS Breakdown & Threat Level

• CVSS Score: 4.9 (Medium)
• Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H
• Attack Vector: Network (AV:N)
• Attack Complexity: Low (AC:L)
• Privileges Required: High (PR:H) – attacker must have administrator credentials.
• User Interaction: None (UI:N)
• Scope: Unchanged (S:U)
• Confidentiality Impact: None (C:N)
• Integrity Impact: None (I:N)
• Availability Impact: High (A:H)

Threat Level: Medium. The requirement for administrator credentials reduces the likelihood of exploitation, but the impact on availability is significant. The lack of a patch increases the risk for unpatched systems.

Deep Dive & Mechanics

The vulnerability resides in an unspecified interface of Dahua products. The exact nature of the crafted data packet is unknown, but it likely exploits a lack of input validation or a buffer overflow condition. When the attacker sends this packet, the device fails to handle it correctly, leading to a crash (denial of service). The crash could be temporary (requiring a reboot) or permanent (requiring hardware replacement).

Root Cause: Improper input validation (CWE-20) in a network-facing interface.

Attack Scenario:

1. Attacker gains administrator credentials (via phishing, brute force, or other means).
2. Attacker sends a crafted data packet to the vulnerable interface.
3. The device crashes, causing a denial of service.

Vulnerable vs. Patched Code

No patch is currently available. The vulnerable code is in the firmware of Dahua devices. Without a patch, the exact vulnerable code cannot be compared.

Exploitation & Lab Setup

Red Team

Objective: Crash a Dahua device to cause a denial of service.

Prerequisites:

• Administrator credentials for the target Dahua device.
• Network access to the device's management interface.

Steps:

1. Reconnaissance: Identify Dahua devices on the network using Shodan or Nmap.

   nmap -p 80,443,554,37777 --open -sV <target_network>
   

2. Credential Access: Obtain administrator credentials (e.g., via brute force or phishing).
3. Craft Payload: Since no public PoC exists, the attacker would need to reverse-engineer the firmware to find the vulnerable interface and craft the payload.
4. Send Payload: Use a tool like curl or a custom script to send the crafted packet.

   curl -X POST -d "malicious_payload" http://<target_ip>/vulnerable_interface
   

5. Verify DoS: The device becomes unresponsive.

Blue Team

Objective: Detect and prevent exploitation of CVE-2024-39945.

Detection:

• Monitor for unusual network traffic to Dahua device management interfaces.
• Look for repeated failed login attempts (indicating credential brute force).
• Monitor device logs for crashes or unexpected reboots.

Prevention:

• Restrict network access to Dahua devices (use firewalls/VLANs).
• Enforce strong, unique passwords for administrator accounts.
• Enable multi-factor authentication (MFA) if supported.
• Monitor for firmware updates from Dahua.

Indicators of Compromise (IOCs)

• Network Traffic: Unusually large or malformed packets sent to port 80, 443, 554, or 37777 on Dahua devices.
• Device Logs: Entries indicating a crash or unexpected reboot.
• System Behavior: Device becomes unresponsive or requires a hard reset.

Detection Engineering

YARA Rule

rule CVE_2024_39945_Dahua_DoS {
    meta:
        description = "Detects potential exploit attempts for CVE-2024-39945 targeting Dahua devices"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2024-39945"
    strings:
        $s1 = "POST" ascii
        $s2 = "/vulnerable_interface" ascii
        $s3 = "malicious" ascii
    condition:
        all of them
}

Sigma Rule

title: CVE-2024-39945 Dahua DoS Exploit Attempt
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects network traffic targeting Dahua devices with potential exploit payloads
author: Valters IT
date: 2025-04-10
logsource:
    category: network_connection
    product: suricata
detection:
    selection:
        dest_port:
            - 80
            - 443
            - 554
            - 37777
        http.method: 'POST'
        http.uri: '/vulnerable_interface'
    condition: selection
falsepositives:
    - Legitimate administrative actions
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET 80,443,554,37777 (msg:"CVE-2024-39945 Dahua DoS Exploit Attempt"; flow:to_server; content:"POST"; http_method; content:"/vulnerable_interface"; http_uri; classtype:attempted-dos; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Restrict Network Access: Use firewalls to limit access to Dahua device management interfaces to trusted IPs only.
2. Change Default Credentials: Ensure all administrator accounts have strong, unique passwords.
3. Monitor for Anomalies: Enable logging and monitor for unusual traffic or device crashes.

Long-Term Actions:

1. Apply Patch: Monitor Dahua's official website for a firmware update that addresses this vulnerability.
2. Upgrade Devices: If no patch is released, consider replacing affected devices with patched alternatives.
3. Implement MFA: If supported, enable multi-factor authentication for administrative access.

Workarounds:

• Disable the vulnerable interface if it is not required for operations.
• Use a VPN or jump host to access management interfaces.

Valters IT signature: This report is provided for educational and defensive purposes only. Unauthorized exploitation of this vulnerability is illegal.