CVE-2022-1438 - Uncovering an XSS Vulnerability in Keycloak's User Impersonation

Keycloak is a widely used, open source identity and access management solution. It powers authentication flows for countless organizations. In 2022, a security flaw—CVE-2022-1438—was discovered. This weakness allows a malicious actor to exploit Keycloak’s user impersonation feature for Cross-site Scripting (XSS). In this article, we’ll break down what this vulnerability is, how it works, and how attackers might use it, all in easy language.

What Is CVE-2022-1438?

In certain scenarios, when an admin impersonates a user in Keycloak, the platform displays user data (including custom attributes) on admin screens. Due to insufficient sanitization, harmful HTML code submitted by a malicious user can be shown directly in the admin’s browser. This can lead to XSS—meaning scripts can run in the admin’s session, opening doors to theft of credentials or further attacks.

Severity: Medium (CVSS 6.1)

How Does the Exploit Work?

1. Attacker Self-Registers an Account: Keycloak setups often allow self-registration, or the attacker finds a way to modify their profile.
2. Attacker Injects Malicious HTML or JS: During the profile update, the attacker puts JavaScript or HTML into fields like firstName, lastName, or a custom attribute.
3. Admin Impersonates the Attacker: The admin uses the impersonation feature to log in as the attacker for troubleshooting or support.
4. XSS Triggered: Unsanitized input gets rendered as actual HTML/JS, executing the attacker's code in the admin’s browser.

Imagine "Eve" is a bad actor who signs up and changes her Keycloak display name to

<script>alert('XSS by Eve');</script>

Whenever an admin impersonates Eve, this script pops an alert on the admin’s screen. Real attackers can use stealthier payloads to steal session tokens or perform malicious actions silently.

How to Test

Here’s a step-by-step demo snippet assuming you have access to a Keycloak account (with public registration):

`html

)">

Relevant Code Snippet

Here’s a *simplified* example of what vulnerable code *could* look like in Java (for educational illustration):

// Hypothetical Keycloak snippet (do not use in production)
String displayName = user.getFirstName();
out.println("<div>Name: " + displayName + "</div>"); // VULNERABLE! No escaping

If displayName includes HTML, it gets rendered unfiltered.

Proper Fix (using JSTL in JSP, for example)

<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core"; %>
<div>Name: <c:out value="${displayName}" /></div>

Or, if using Java

out.println("<div>Name: " + HtmlUtils.htmlEscape(displayName) + "</div>");

Mitigation and Patch

- Upgrade: The Keycloak security advisory says this XSS flaw is patched in Keycloak v18.. and later.

References and Further Reading

- Keycloak Advisory: Security Bulletin 2022-02
- NVD National Vulnerability Database CVE-2022-1438
- OWASP XSS Prevention Cheat Sheet

Conclusion

CVE-2022-1438 is a reminder that even trusted management tools need robust input sanitization. Admin features like impersonation can become attack vectors if HTML entities aren’t safely handled. If you use Keycloak, update to the latest version and audit any area where user-input is rendered in the admin interface. Stay safe!


*Have questions or need a deeper code walk-through? Drop your comments below!*

Timeline

Published on: 09/20/2023 14:15:00 UTC
Last modified on: 09/25/2023 13:40:00 UTC