The Watchman Sleeps: Piercing WatchGuard Fireware via LDAP Injection

There is a delicious irony in finding holes in security appliances. You buy a WatchGuard Firebox to keep the bad guys out, to stand as the sentinel at the edge of your network. But in the case of CVE-2026-1498, the sentinel is a bit tipsy and prone to listening to gossip.

This vulnerability isn't some complex heap overflow requiring a Ph.D. in memory management. It's a classic logic flaw in how the Fireware OS talks to its backend. Specifically, it involves the management and authentication interfaces—the very portals you use to administer the device. When configured to use an external authentication server (like Active Directory via LDAP), the device acts as a proxy.

Here is the problem: The device trusts you too much. When you type your username, it takes that string, blindly assumes you're a civilized human being who wouldn't use special characters, and pastes it directly into an LDAP query. If you've ever dealt with SQL injection, you know where this is going. But in the world of LDAP, the syntax is different, the trees are hierarchical, and the impact is often subtler but just as devastating.

LDAP (Lightweight Directory Access Protocol) is the language of phonebooks. It uses a specific syntax to find things, relying heavily on parentheses () to group logic and characters like * for wildcards. A typical query to find a user looks like this: (&(uid=jdoe)(objectClass=person)).

In a secure application, the inputs jdoe would be sanitized. The characters (, ), *, \, and NUL would be escaped, turning them into harmless text literals. WatchGuard, however, skipped this step in Fireware OS versions leading up to 2026. They essentially took the input buffer and concatenated it into the filter string.

This is the "Bobby Tables" of the directory world. Because the application doesn't neutralize special elements (CWE-90), the query structure itself becomes mutable. The code effectively says, "Find me the user whose name is [WHATEVER THE ATTACKER TYPED]." By typing admin*, the query changes from an exact match to a prefix match. By typing *)(objectClass=*, the attacker can close the original logic and start a new, broader search.

While we don't have the exact proprietary source code from the Firebox firmware, we can reconstruct the logic based on the behavior and the patch analysis. The vulnerability resides in the authentication daemon's handling of the username POST parameter.

The Vulnerable Logic (Pseudo-code):

// The developer assumes 'username' is just alphanumeric
char query[256];
snprintf(query, sizeof(query), "(&(uid=%s)(objectClass=inetOrgPerson))", username_input);
 
// If username_input is "admin*", the query becomes:
// (&(uid=admin*)(objectClass=inetOrgPerson))
// This is valid LDAP syntax! It asks for any uid starting with 'admin'.

The flaw is the direct interpolation of username_input into the filter string. There is no ldap_escape_filter_value() function being called here.

The Fix:

To remediate this, the input must be encoded. In a proper implementation, special characters are converted to their hex representation (e.g., * becomes \2a).

// The Fixed Logic
char *escaped_username = ldap_escape_filter_value(username_input);
snprintf(query, sizeof(query), "(&(uid=%s)(objectClass=inetOrgPerson))", escaped_username);
 
// Now, if input is "admin*", the query becomes:
// (&(uid=admin\2a)(objectClass=inetOrgPerson))
// The server looks for a literal asterisk in the name, which fails safely.

This simple omission of an escape function turns a routine login form into a database query tool for attackers.

How do we weaponize this? We likely can't see the results of the LDAP query directly on the login page (it just says "Login Failed" or "Success"). However, we can use Blind LDAP Injection to infer data based on the server's response time or error messages.

Phase 1: Authentication Bypass

If the application logic allows the first result returned by LDAP to bind, we can try to log in as admin without knowing the exact username syntax (e.g., is it admin, administrator, admin_local?).

• Payload: User: admin* / Pass: [Bruteforce]
• Result: The wildcard matches administrator. If we guess the password, we are in, even if we didn't know the account was named administrator.

Phase 2: Directory Mapping (The Real Danger)

We can extract data by asking True/False questions. Let's say we want to find if a user exists with a phone number starting with 555.

• Injection: admin)(telephoneNumber=555*
• Resulting Query: (&(uid=admin)(telephoneNumber=555*))

If the login takes slightly longer (processing the query) or returns a specific "Invalid Password" error (meaning the User was found, but password failed), we know the condition is TRUE. If it returns "User not found," the condition is FALSE.

We can script this to iterate through characters:

1. admin)(userPassword=a* -> False
2. admin)(userPassword=b* -> False
3. admin)(userPassword=s* -> True (Ah, the password starts with 's'!).

This allows us to exfiltrate data byte-by-byte without ever successfully logging in.

Why is this a high-severity issue if it requires a password to fully log in, or tedious scripting to extract data? Because the Firebox sits at a privileged position in the network. It is trusted.

1. Internal Network Mapping: The Firebox is often connected to the corporate Active Directory. By exploiting this, I am effectively querying your Domain Controller from the internet, bypassing your perimeter firewall (because I am the firewall).

2. Account harvesting: I can enumerate valid usernames, email addresses, and group memberships. This is gold for a follow-up phishing campaign. "Hey Bob from Accounting" is a lot more convincing when I know Bob actually exists and is in the Accounting group.

3. Denial of Service: LDAP supports recursive queries. A complex injection like (|(uid=*)...(repeat 1000 times)) could force the backend LDAP server to burn CPU cycles trying to parse the logic, effectively DoS-ing the authentication for the entire enterprise.

If you are running WatchGuard Fireware, stop reading and check your version. If you are on the 12.x branch or early 2025/2026 builds, you are likely exposed.

Primary Mitigation: Patch Immediately

WatchGuard has released fixes in versions 12.11.7, 12.5.16, and 2026.1. These updates implement proper input sanitization libraries that escape special LDAP characters before query construction.

Secondary Mitigation: Access Control

Why is your management interface exposed to the internet? Seriously, why?

1. VPN Only: Restrict the management UI (port 8080/4100) to internal interfaces or VPN users only.
2. IP Allowlisting: If you must expose it, whitelist the specific IPs of your admins.

Defensive Monitoring

Configure your SIEM to flag any authentication attempts containing characters like *, (, or ). A username should generally be alphanumeric. If you see admin* in your logs, someone is knocking.