How to remediate – Western Digital MyCloud Unauthenticated File Upload

1. Introduction

The Western Digital MyCloud Unauthenticated File Upload vulnerability allows a remote attacker to upload and execute files on affected devices. This poses a significant risk to data confidentiality, integrity, and availability as attackers can gain control of the device and potentially access or modify stored data. Systems commonly affected are Western Digital MyCloud NAS devices running vulnerable firmware versions. A successful exploit could lead to complete system compromise.

2. Technical Explanation

This vulnerability stems from a lack of authentication checks on the file upload functionality within the WD MyCloud device’s web interface. An attacker can bypass security measures and upload malicious files, which are then executed by the server. The CVE associated with this issue is CVE-2017-17560. For example, an attacker could upload a PHP shell to gain remote code execution on the MyCloud device.

• Root cause: missing authentication for file uploads.
• Exploit mechanism: An attacker sends a crafted HTTP request containing malicious files directly to the vulnerable endpoint without needing valid credentials.
• Scope: Western Digital MyCloud devices running firmware versions prior to 2.30.174 are affected.

3. Detection and Assessment

You can confirm vulnerability by checking the installed firmware version on your MyCloud device. A thorough assessment involves attempting a test upload of a known malicious file.

• Quick checks: Access the MyCloud web interface, navigate to Settings > Firmware Update, and check the current version.
• Scanning: Nessus plugin ID 108697 can detect this vulnerability as an example.
• Logs and evidence: Check system logs for unusual file upload activity or errors related to file processing. Specific log paths vary by MyCloud model.

curl -I http://[MyCloud IP Address]/api/v2/upload #Check if the endpoint responds without authentication

4. Solution / Remediation Steps

The following steps outline how to fix this vulnerability by updating your MyCloud device’s firmware.

4.1 Preparation

• No services need stopping, but plan for potential downtime during the update process.
• Roll back is possible by restoring from backup or reverting to a previous firmware version (if available).

4.2 Implementation

1. Step 1: Download the latest firmware version from Western Digital’s support website (https://www.westerndigital.com/support).
2. Step 2: Log in to the MyCloud web interface as an administrator.
3. Step 3: Navigate to Settings > Firmware Update.
4. Step 4: Select “Check for Updates”.
5. Step 5: If a new version is available, select it and begin the update process.

4.3 Config or Code Example

Before

N/A - This vulnerability is due to missing authentication, not a specific configuration setting.

After

Firmware version 2.30.174 or later should be installed. Verify via Settings > Firmware Update in the web interface.

4.4 Security Practices Relevant to This Vulnerability

Several security practices can help prevent this type of issue. Least privilege limits damage from exploitation, and input validation blocks unsafe data uploads. A regular patch cadence ensures timely fixes are applied.

• Practice 1: Implement least privilege principles by restricting user access to only the necessary resources.
• Practice 2: Enforce strict input validation on all file upload forms to prevent malicious files from being uploaded.

4.5 Automation (Optional)

Automation is unlikely for this specific vulnerability due to the manual update process required by Western Digital’s firmware system.

N/A - Firmware updates are typically performed manually through the web interface.

5. Verification / Validation

• Post-fix check: Access Settings > Firmware Update in the web interface; the version should be 2.30.174 or later.
• Re-test: Repeat the curl command from the detection phase; it should now return an authentication error (e.g., 401 Unauthorized).
• Smoke test: Verify you can still access and download files stored on the MyCloud device.
• Monitoring: Check system logs for failed file upload attempts, which would indicate a potential attack attempt.

curl -I http://[MyCloud IP Address]/api/v2/upload #Should return 401 Unauthorized after update

6. Preventive Measures and Monitoring

Regularly updating security baselines to include the latest firmware versions is important for preventing this issue. Incorporate vulnerability scanning into your CI or deployment pipelines, and establish a sensible patch review cycle based on risk.

• Baselines: Update your security baseline to require MyCloud devices to run firmware version 2.30.174 or later.
• Asset and patch process: Review and apply firmware updates at least quarterly, or sooner for critical vulnerabilities.

7. Risks, Side Effects, and Roll Back

• Risk or side effect 1: Firmware update failure could render the device unusable; ensure a stable power supply during the process.
• Roll back: Restore from backup, or attempt to revert to the previous firmware version via the web interface (if supported).

8. References and Resources

• Vendor advisory or bulletin: https://www.westerndigital.com/support
• NVD or CVE entry: CVE-2017-17560
• Product or platform documentation relevant to the fix: https://www.exploitee.rs/index.php/Western_Digital_MyCloud