Unauthenticated Blind Server-Side Request Forgery Vulnerability (SSRF)

Unauthenticated Blind Server-Side Request Forgery Vulnerability (SSRF)

WordPress <= 6.4.3 – Unauthenticated Blind Server-Side Request Forgery vulnerability (SSRF)

What is SSRF?

A blind server-side request forgery (SSRF) vulnerability in WordPress Core could potentially allow an attacker to make unauthorized requests from the server to internal or external resources, bypassing security mechanisms and potentially accessing sensitive information or executing arbitrary code. Simon Scannell & Thomas Chauchefoin discovered and reported this Server Side Request Forgery (SSRF) vulnerability in WordPress.

How to mitigate the risk associated with SSRF vulnerabilities?

To mitigate the risk associated with such vulnerabilities, it’s crucial to follow security best practices:

  1. Keep WordPress Up to Date: Always ensure that your WordPress installation, including themes and plugins, is updated to the latest version. Developers often release security patches to address vulnerabilities.
  2. Implement Web Application Firewall (WAF): Utilize a WAF to monitor and filter incoming HTTP traffic to your WordPress site. A WAF can help detect and block malicious requests, including SSRF attempts.
  3. Restrict File Permissions: Limit the permissions of files and directories within your WordPress installation to prevent unauthorized access. Ensure that sensitive files are not publicly accessible.
  4. Use Security Plugins: Install reputable security plugins that can help identify and mitigate common security risks, including SSRF vulnerabilities.
  5. Monitor Server Logs: Regularly monitor server logs for unusual or suspicious activity, including unauthorized requests originating from the server.
  6. Implement Content Security Policy (CSP): Consider implementing a CSP to restrict the sources from which content can be loaded on your website, mitigating the risk of XSS attacks and potentially limiting the impact of SSRF vulnerabilities.
  7. Educate Users: Educate users, especially administrators and content editors, about security best practices, such as avoiding clicking on suspicious links or downloading files from unknown sources.
  8. Stay Informed: Stay informed about security advisories and vulnerabilities related to WordPress Core and third-party plugins and themes. Subscribe to security mailing lists and follow reputable security researchers and organizations for updates.

Simulate the behavior of an SSRF attack in a controlled environment:

$url = $_GET['url'];

// Check if the URL is valid (for demonstration purposes only)
if (filter_var($url, FILTER_VALIDATE_URL)) {
    // In a real SSRF scenario, this would be the part where the URL is fetched
    // For demonstration purposes, we'll just echo the URL
    echo "Requested URL: " . $url;
} else {
    echo "Invalid URL";

If you suspect that your WordPress site is vulnerable to SSRF or any other security issue, it’s essential to take immediate action to mitigate the risk. This may involve implementing temporary mitigations, such as blocking specific requests or disabling vulnerable features, until a permanent fix can be applied. Additionally, consider engaging with security professionals or organizations with expertise in WordPress security for assistance.