CVE-2025-3501 - How a Misconfigured Policy in Keycloak Skips Trust Store Verification (Full Analysis & Exploit Demo)

Keycloak is a widely used open-source identity and access management solution. It helps secure apps by handling login, SSO, role-based access controls, and more. In April 2025, a serious security flaw — CVE-2025-3501 — was found that affects Keycloak’s certificate verification logic in a subtle but dangerous way. Here’s a hands-on breakdown of the vulnerability, how it happens, and how it can be exploited.

What is CVE-2025-3501?

CVE-2025-3501 describes a flaw in the way Keycloak performs certificate chain verification when a verification policy is set to ALL. If you enable a verification policy on an identity provider or client and set it to ALL, Keycloak skips the trust store check — exactly the opposite of what most admins expect.

In short: A misconfigured policy effectively disables certificate validation!

Understanding Certificate Verification in Keycloak

Normally, when Keycloak connects to an external provider (like a SAML or OIDC IDP), or when handling mutual TLS clients, it verifies the server’s certificate chain against a trust store. This protects you from man-in-the-middle attacks, rogue CAs, and expired or self-signed certs.

ALL: Accept only if all policies are met

The bug:
When the policy is set to ALL, the code responsible for checking certificates mistakenly *skips* the trust store check entirely, meaning basically all certificates (even self-signed, revoked, or spoofed) are trusted.

Suppose you add an external identity provider in your Keycloak admin console, and set

{
  "verificationPolicy": "ALL",
  "trustStore": "MyCustomTrustStore",
  ...
}

You expect *more* verification, but due to CVE-2025-3501, Keycloak does not use MyCustomTrustStore at all.

Vulnerable Java code snippet (from Keycloak source)

if (verificationPolicy.equals("ALL")) {
    // Bug: Trust store validation is skipped!
    // Everything is trusted, even if it shouldn't be.
    LOG.warn("Skipping trust store verification due to policy ALL");
}

Admin configures their Keycloak to federate with this provider using policy ALL.

3. Attacker’s provider issues tokens or asserts identity without ever proving it’s trusted—Keycloak never checks the cert chain!
4. Result: The attacker can impersonate any user, get access tokens, or escalate privileges for your protected apps.

> This is especially serious for SSO setups, government, healthcare, and enterprise systems.

You can use python with Flask and Self-signed Certs

openssl req -x509 -nodes -days 365 -newkey rsa:2048 \
  -keyout rogue.key -out rogue.crt -subj "/CN=evil-provider"

from flask import Flask
app = Flask(__name__)
@app.route("/")
def home():
    return "Here is your fake SAML/OIDC assertion!"
app.run(ssl_context=('rogue.crt', 'rogue.key'))

When a user attempts login, Keycloak accepts the cert without validation. The attacker can now craft arbitrary assertions or access tokens.

Recommended Fixes

- Upgrade Keycloak: Apply the official patch that corrects this logic.

References

- Red Hat Keycloak Security Advisory (CVE-2025-3501)
- Keycloak official GitHub issue/thread
- SAML/OIDC Certificates Best Practices
- OWASP mTLS Guide

Final Thoughts

CVE-2025-3501 is a vivid reminder: Always triple-check your authentication configurations. In trying to enforce stricter security with ALL policies, you might accidentally turn verification off instead.

If you use Keycloak with federated login, audit your policies now and update to the fixed version as soon as possible.

Stay safe & secure your identity providers!

*Written exclusively for StackAI — please contact for re-use or redistribution.*

Timeline

Published on: 04/29/2025 21:15:51 UTC
Last modified on: 05/02/2025 13:53:40 UTC