How to remediate – Visual Studio Code Server Files Detected

1. Introduction

Visual Studio Code Server Files Detected refers to the presence of files associated with Microsoft’s Visual Studio Code server on a system, typically created when using remote workspace access via SSH. This can expose sensitive information like user activity, binaries and scripts, potentially facilitating attacks against the server. Confidentiality, integrity, and availability may be impacted if an attacker gains access to these files or uses them to compromise the system.

2. Technical Explanation

Visual Studio Code’s remote workflow creates a hidden directory named .vscode-server on the remote server. This directory stores configuration files, extensions and other data necessary for the remote development environment. If web application configurations allow access to this directory, sensitive information within it may be exposed. An attacker could exploit this by accessing these files to gain insights into the system’s configuration or execute malicious scripts.

• Root cause: The .vscode-server directory is created with potentially insecure default permissions and accessible via web server configurations.
• Exploit mechanism: An attacker gains access to the .vscode-server directory through a misconfigured web server, allowing them to read sensitive files or execute scripts within it. For example, an attacker could use a browser to navigate to the directory if it’s publicly accessible.
• Scope: Systems running Visual Studio Code Server with remote SSH access enabled are affected.

3. Detection and Assessment

Confirming vulnerability involves checking for the presence of the .vscode-server directory and assessing its accessibility. A quick check can identify the directory, while a thorough method will assess file permissions.

• Quick checks: Use the following command to list directories in the user’s home folder. Look for the existence of ‘.vscode-server’.
• Scanning: Nessus plugin 16879 may detect exposed .vscode-server files, but results should be verified manually.
• Logs and evidence: Web server access logs should be reviewed for requests to the .vscode-server directory.

ls -la ~

4. Solution / Remediation Steps

Fixing this issue requires reviewing the contents of the .vscode-server directory and removing sensitive content, or adjusting web server access controls to limit exposure.

4.1 Preparation

• Ensure you have SSH access to the server for rollback purposes. A roll back plan involves restoring the backup or restarting the web server service.
• Changes should be made during a scheduled maintenance window with appropriate approval from system owners.

4.2 Implementation

1. Step 1: Check if the .vscode-server directory exists in user home directories.
2. Step 2: If present, review the contents of the .vscode-server directory for sensitive information such as configuration files or scripts.
3. Step 3: Remove any unnecessary or sensitive files from the .vscode-server directory.
4. Step 4: Adjust web server access controls to restrict access to the .vscode-server directory, preventing public access.

4.3 Config or Code Example

Before

# Apache example - allowing access from all IPs
<Directory /home/user/.vscode-server>
    Options Indexes FollowSymLinks
    AllowOverride None
    Require all granted
</Directory>

After

# Apache example - restricting access to specific IPs or localhost only
<Directory /home/user/.vscode-server>
    Options Indexes FollowSymLinks
    AllowOverride None
    Require local
</Directory>

4.4 Security Practices Relevant to This Vulnerability

List only practices that directly address this vulnerability type. Use neutral wording and examples instead of fixed advice. For example: least privilege, input validation, safe defaults, secure headers, patch cadence.

• Practice 1: Least privilege access control reduces the impact if an attacker gains access to sensitive files.
• Practice 2: Secure configuration management ensures web servers are not misconfigured allowing unintended access to sensitive directories.

4.5 Automation (Optional)

#!/bin/bash
# Script to restrict access to .vscode-server directories in Apache configuration
for user in $(cut -d: -f1 /etc/passwd); do
  if [ -d "/home/$user/.vscode-server" ]; then
    sed -i 's/^Require all granted/Require local/' /etc/apache2/sites-available/*.conf #Risky, review config files before running.
  fi
done
systemctl restart apache2

5. Verification / Validation

Confirming the fix involves checking that access to the .vscode-server directory is restricted and verifying system functionality.

• Post-fix check: Attempt to access the .vscode-server directory via a web browser. Expect a 403 Forbidden error.
• Re-test: Re-run the `ls -la ~` command from step 3 of Detection and Assessment to confirm the directory still exists, but is no longer accessible through the web server.
• Monitoring: Monitor web server logs for any attempts to access the .vscode-server directory.

curl http://your_server/.vscode-server -I # Expect 403 Forbidden

6. Preventive Measures and Monitoring

Suggest only measures that are relevant to the vulnerability type. Use “for example” to keep advice conditional, not prescriptive.

• Baselines: Update security baselines or policies to include restrictions on access to hidden directories like .vscode-server.
• Pipelines: Implement static analysis tools in CI/CD pipelines to identify insecure configurations and prevent deployment of misconfigured web servers.
• Asset and patch process: Review server configurations regularly as part of a vulnerability management program.

7. Risks, Side Effects, and Roll Back

• Risk or side effect 1: Restricting access too broadly may impact legitimate users accessing other resources on the server.
• Risk or side effect 2: Incorrect web server configuration changes could lead to service downtime.
• Roll back: Restore the original web server configuration file from backup, then restart the web server service.

8. References and Resources

• Vendor advisory or bulletin: https://code.visualstudio.com/docs/remote/ssh
• NVD or CVE entry: No specific CVE is associated with this issue, but it relates to common web server misconfiguration vulnerabilities.
• Product or platform documentation relevant to the fix: Apache HTTP Server documentation on access control configuration.