CVE-2024-39946

Executive Summary

CVE-2024-39946 is a vulnerability in Dahua products that allows an authenticated attacker (with administrator credentials) to send a crafted data packet to a vulnerable interface, causing device initialization. This effectively resets the device to factory defaults, leading to a denial of service (DoS) and potential loss of configuration. The vulnerability has a CVSS score of 6.0 (Medium) and is currently unpatched. No public exploit code or proof-of-concept is available, but the attack vector is clear: an attacker with admin access can trigger a factory reset remotely.

Note: This vulnerability is not related to any open-source package (NPM, PyPI, Go, Ruby) and does not involve a WordPress plugin. It is a proprietary IoT/embedded device vulnerability.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:H/A:H
• Base Score: 6.0 (Medium)
• Attack Vector: Network (AV:N) – exploitable remotely.
• Attack Complexity: Low (AC:L) – no special conditions required.
• Privileges Required: High (PR:H) – attacker must have administrator credentials.
• User Interaction: None (UI:N) – no user action needed.
• Scope: Unchanged (S:U) – impact confined to the vulnerable component.
• Confidentiality Impact: None (C:N) – no data exposure.
• Integrity Impact: High (I:H) – device configuration is destroyed.
• Availability Impact: High (A:H) – device becomes unusable until reconfigured.

Threat Level: Medium. The requirement for admin credentials reduces the likelihood of widespread exploitation, but the impact is severe for targeted attacks.

Deep Dive & Mechanics

The vulnerability resides in a specific API endpoint or interface used for device management. After authentication, the attacker sends a specially crafted data packet (likely a malformed HTTP request or a specific command) that triggers the device’s initialization routine. This routine is intended for factory reset or first-time setup, but the input validation is insufficient, allowing an authenticated user to invoke it arbitrarily.

Root Cause: Improper input validation (CWE-20) in the device’s web interface or management API. The endpoint does not verify that the request is legitimate (e.g., requiring a physical button press or a separate authorization token).

Attack Flow:

1. Attacker obtains admin credentials (via phishing, default passwords, or other means).
2. Attacker sends a crafted packet to the vulnerable endpoint (e.g., /cgi-bin/init.cgi or similar).
3. Device executes initialization, wiping all settings and rebooting to factory defaults.
4. Device becomes inaccessible until reconfigured, causing DoS.

Vulnerable vs. Patched Code

No patch is available. The vulnerable code likely resembles:

# Vulnerable pseudo-code
def handle_init_request(request):
    if request.method == "POST" and request.user.is_admin:
        # No additional validation
        device.factory_reset()
        return "OK"

A patched version would require:

# Patched pseudo-code
def handle_init_request(request):
    if request.method == "POST" and request.user.is_admin:
        if request.headers.get("X-Init-Token") != SECRET_TOKEN:
            return "Forbidden", 403
        device.factory_reset()
        return "OK"

Exploitation & Lab Setup

Red Team

Prerequisites:

• Admin credentials for a Dahua device.
• Network access to the device’s web interface (typically port 80 or 443).

Exploitation Steps:

1. Authenticate to the device’s web interface.
2. Identify the vulnerable endpoint (e.g., via fuzzing or known patterns like /cgi-bin/init.cgi).
3. Send a crafted POST request with the admin session cookie.

Example using curl:

curl -X POST http://<device_ip>/cgi-bin/init.cgi \
  -H "Cookie: session=<admin_session>" \
  -d "action=reset"

Note: No public exploit code exists; this is a hypothetical example based on the description.

Blue Team

Detection:

• Monitor for unusual POST requests to device management endpoints.
• Alert on multiple failed login attempts followed by a successful admin login and a subsequent reset request.
• Use network monitoring to detect anomalous packets targeting /cgi-bin/ paths.

Prevention:

• Enforce strong, unique passwords for admin accounts.
• Disable remote management if not required.
• Implement network segmentation to limit access to IoT devices.
• Use a WAF to block malformed requests to management interfaces.

Indicators of Compromise (IOCs)

• Network IOCs:

  • POST requests to /cgi-bin/init.cgi or similar reset endpoints.
  • Unusual HTTP headers or payloads containing action=reset or factory_reset.
  • Traffic from an IP address that recently performed a successful admin login.

• Host IOCs:

  • Device logs showing a factory reset event without physical interaction.
  • Device reboot logs coinciding with the attack time.

• File IOCs:

  • No file-based IOCs; this is a network-based attack.

Detection Engineering

YARA Rule

rule CVE_2024_39946_Dahua_Init_Exploit {
    meta:
        description = "Detects crafted packets targeting Dahua device initialization endpoint"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2024-39946"
    strings:
        $init_path = "/cgi-bin/init.cgi" nocase
        $reset_action = "action=reset" nocase
        $factory_reset = "factory_reset" nocase
    condition:
        any of them
}

Sigma Rule

title: Dahua Device Initialization Exploit Attempt
id: 8a9b3c2d-1e5f-4a7b-8c9d-0e1f2a3b4c5d
status: experimental
description: Detects HTTP POST requests to Dahua device initialization endpoints
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        cs-uri-stem: '/cgi-bin/init.cgi'
        cs-uri-query|contains: 'action=reset'
    condition: selection
falsepositives:
    - Legitimate admin actions (rare)
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2024-39946 Dahua Device Initialization Attempt"; flow:to_server; content:"POST"; http_method; content:"/cgi-bin/init.cgi"; http_uri; content:"action=reset"; http_client_body; classtype:attempted-dos; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Change all default admin passwords to strong, unique passwords.
2. Disable remote web access to Dahua devices if not essential.
3. Restrict access to the management interface via firewall rules (allow only trusted IPs).

Long-Term Fix:

• Vendor must release a firmware update that adds additional validation (e.g., a confirmation token or physical button press) before executing a factory reset.
• Until a patch is available, monitor logs for suspicious activity and consider replacing affected devices.

Workaround:

• Use a reverse proxy or WAF to block requests to /cgi-bin/init.cgi unless they come from a whitelisted IP.

Valters IT