The Infinite Keyring: Brute-Forcing WildFly Elytron (CVE-2025-23368)

Authentication is the bouncer of your application. Ideally, if someone tries to guess the secret password and fails ten times in a row, the bouncer should throw them out—or at least make them wait in the parking lot for a few minutes. This is Security 101. It's the difference between a secure system and a slot machine that lets you pull the lever until you win.

WildFly, the upstream project for Red Hat JBoss EAP, uses a security framework called Elytron. Elytron is powerful, modular, and flexible. But as it turns out, in certain configurations—specifically when using the Management Interface—Elytron was a bouncer with amnesia. It didn't care if you failed the password check a thousand times per second. It would just politely say "No" and immediately let you try again. No lockout. No delay. No penalty.

For a hacker, this is the golden ticket. Brute-forcing is usually a noisy, slow game of cat and mouse where you try to stay under the radar of WAFs and account lockouts. But with CVE-2025-23368, the radar didn't exist. You could effectively point a firehose of credentials at port 9990 and wait for the "HTTP 200 OK".

To understand the bug, you have to understand the architecture. Elytron uses Security Realms to handle identity. You might have a PropertiesRealm (users in a file), LdapRealm, or a JdbcRealm. To speed things up, especially for expensive lookups like LDAP, administrators often wrap these in a CachingRealm.

The CachingRealm is great at remembering successes. If admin logs in successfully, Elytron caches that identity so it doesn't have to query the database again for a while. Optimization is good, right?

Here is the cynical twist: The CachingRealm (and the default configuration for the management interface) was optimized for performance, not resilience. It remembered friends, but it had no mechanism to track enemies. When an authentication attempt failed, the system simply returned a failure response and moved on. There was no counter being incremented, no last_failed_timestamp being checked. The state machine for failure was effectively non-existent.

> [!NOTE] > The Architectural Gap > The vulnerability wasn't a buffer overflow or a logic error in password comparison. It was a missing feature treated as a security flaw. The code simply presumed that the underlying realm or an external firewall would handle the rate limiting. That is a dangerous assumption in 2025.

Let's look at the "Smoking Gun". The fix didn't involve rewriting the authentication logic; it involved wrapping it. The developers realized they needed to implement the Decorator Pattern to intercept authentication calls and apply physics (i.e., time delays) to them.

In the patch (Commit 11e873031c522a0b36afb59880ce4dd59efd0bc0), a new concept was introduced: the BruteForceRealmWrapper. This wrapper sits between the network interface and the actual Security Realm.

Here is a conceptual simplification of what was added:

// The new wrapper logic (simplified)
public RealmIdentity getRealmIdentity(Principal principal) throws RealmUnavailableException {
    // 1. Check if this user is already locked out
    if (isLockedOut(principal)) {
        throw new RealmUnavailableException("Account locked due to too many failures");
    }
 
    // 2. Attempt the actual authentication via the underlying realm
    RealmIdentity identity = delegate.getRealmIdentity(principal);
 
    // 3. If successful, clear previous failures
    if (identity.verifyCredentials(credential)) {
        clearFailures(principal);
        return identity;
    } else {
        // 4. If failed, increment counter and potentially lock
        incrementFailureCount(principal);
        return null;
    }
}

Before this patch, the code essentially jumped straight to step 2. If the verification failed, it just returned null or threw an exception, and the server was ready for the next request 0.001ms later. The patch forces every request through a transformer that says, "Hold on, have you failed 5 times in the last minute? If so, come back later."

Exploiting this is trivially easy because the target is the Management Interface, typically listening on TCP port 9990. This port speaks HTTP (for the web console) and a native Remoting protocol. Both are susceptible.

An attacker doesn't need complex memory corruption exploits here. They just need a dictionary and a loop. Since there is no lockout, we can use a multi-threaded script to blast credentials.

Attack Scenario

1. Recon: Scan for open port 9990. Identify the header Server: WildFly.
2. Weaponization: Create a list of common credentials (admin:admin, admin:password, jboss:jboss).
3. Execution: Launch the attack using a tool like Hydra or a custom Python script using requests. Since the server doesn't throttle us, we can easily hit 50-100 requests per second depending on network latency.

Because the vulnerability allows parallel attempts (if the server has the threads for it), a distributed botnet could theoretically try millions of passwords an hour against a high-value target.

Why is this CVSS 8.1 and not lower? Because access to the WildFly Management Interface is effectively Remote Code Execution (RCE) as a Service.

Once an attacker guesses the credential:

1. Deployment: They can deploy a malicious .war file (Web Application Archive) containing a webshell (like the classic JSP shells).
2. Configuration: They can modify data sources to point to malicious database servers, stealing application data.
3. System Access: Since WildFly often runs with high privileges (or effectively as the user owning the data), the attacker now owns the data.

This isn't just about reading logs. It's about full compromises of the application server. The lack of rate limiting transforms a "weak password" problem into a "guaranteed entry" problem given enough time.

Red Hat patched this in WildFly Core 31.0.3 and associated JBoss EAP versions. The fix isn't just a hardcoded limit; it's a configurable subsystem.

If you are running an affected version, patch immediately. Once patched, you should actually configure the new brute-force detection, because defaults are great, but tuned security is better.

New Configuration Options:

• wildfly.elytron.realm.<name>.brute-force.max-failed-attempts: Set this to something reasonable, like 5 or 10.
• wildfly.elytron.realm.<name>.brute-force.lockout-interval: How long to ban them? 15 minutes (900000 ms) is standard.

Workaround (If you can't patch): If you are stuck on legacy code, you need to move the protection upstream. Put your Management Interface behind a VPN. Never, ever expose port 9990 to the internet. If you must expose it, put it behind a reverse proxy (like Nginx or HAProxy) configured with strict limit_req zones to drop traffic from aggressive IPs.