In case when LdapExtLoginModule is correctly configured for authentication, but its attributes rolesCtxDN and roleFilter are not set, then authentication with correct username and password leads to FailedLoginException.
Expected behavior is that user should be authenticated but no roles should be assigned to them.
Possible EAP configuration:
<security-domain name="ldap">
<authentication>
<login-module code="org.jboss.security.auth.spi.LdapExtLoginModule" flag="required">
<module-option name="baseFilter" value="(uid=

{0})"/>
<module-option name="bindDN" value="uid=admin,ou=system"/>
<module-option name="baseCtxDN" value="ou=People,o=MyOrg,o=primary,dc=jboss,dc=org"/>
<module-option name="java.naming.factory.initial" value="com.sun.jndi.ldap.LdapCtxFactory"/>
<module-option name="java.naming.security.authentication" value="simple"/>
<module-option name="java.naming.provider.url" value="ldap://localhost:10389"/>
<module-option name="bindCredential" value="secret"/>
</login-module>
</authentication>
</security-domain>

In case when these attributes are added
<module-option name="rolesCtxDN" value="ou=Roles,o=MyOrg,o=primary,dc=jboss,dc=org"/>
<module-option name="roleFilter" value="(member={0}

)"/>
then user is correctly authenticated (even in case when no role is assigned to them).
It is caused by internal NPE thrown from method rolesSearch in LdapExtLoginModule class on line:
results = ldapCtx.search(rolesCtxDN, roleFilter, filterArgs, constraints);
DEBUG [org.jboss.security] (default task-2) PBOX000206: Login failure: javax.security.auth.login.FailedLoginException: PBOX000070: Password invalid/Password required
at org.jboss.security.auth.spi.UsernamePasswordLoginModule.login(UsernamePasswordLoginModule.java:284)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at javax.security.auth.login.LoginContext.invoke(LoginContext.java:762)
at javax.security.auth.login.LoginContext.access$000(LoginContext.java:203)
at javax.security.auth.login.LoginContext$4.run(LoginContext.java:690)
at javax.security.auth.login.LoginContext$4.run(LoginContext.java:688)
at java.security.AccessController.doPrivileged(Native Method)
at javax.security.auth.login.LoginContext.invokePriv(LoginContext.java:687)
at javax.security.auth.login.LoginContext.login(LoginContext.java:595)
at org.jboss.security.authentication.JBossCachedAuthenticationManager.defaultLogin(JBossCachedAuthenticationManager.java:411)
at org.jboss.security.authentication.JBossCachedAuthenticationManager.proceedWithJaasLogin(JBossCachedAuthenticationManager.java:350)
at org.jboss.security.authentication.JBossCachedAuthenticationManager.authenticate(JBossCachedAuthenticationManager.java:338)
at org.jboss.security.authentication.JBossCachedAuthenticationManager.isValid(JBossCachedAuthenticationManager.java:148)
at org.wildfly.extension.undertow.security.JAASIdentityManagerImpl.verifyCredential(JAASIdentityManagerImpl.java:111)
at org.wildfly.extension.undertow.security.JAASIdentityManagerImpl.verify(JAASIdentityManagerImpl.java:82)
at io.undertow.security.impl.BasicAuthenticationMechanism.authenticate(BasicAuthenticationMechanism.java:118)
at io.undertow.security.impl.SecurityContextImpl$AuthAttempter.transition(SecurityContextImpl.java:339)
at io.undertow.security.impl.SecurityContextImpl$AuthAttempter.transition(SecurityContextImpl.java:356)
at io.undertow.security.impl.SecurityContextImpl$AuthAttempter.access$100(SecurityContextImpl.java:325)
at io.undertow.security.impl.SecurityContextImpl.attemptAuthentication(SecurityContextImpl.java:138)
at io.undertow.security.impl.SecurityContextImpl.authTransition(SecurityContextImpl.java:113)
at io.undertow.security.impl.SecurityContextImpl.authenticate(SecurityContextImpl.java:106)
at io.undertow.servlet.handlers.security.ServletAuthenticationCallHandler.handleRequest(ServletAuthenticationCallHandler.java:55)
at io.undertow.server.handlers.DisableCacheHandler.handleRequest(DisableCacheHandler.java:33)
at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
at io.undertow.security.handlers.AuthenticationConstraintHandler.handleRequest(AuthenticationConstraintHandler.java:51)
at io.undertow.security.handlers.AbstractConfidentialityHandler.handleRequest(AbstractConfidentialityHandler.java:46)
at io.undertow.servlet.handlers.security.ServletConfidentialityConstraintHandler.handleRequest(ServletConfidentialityConstraintHandler.java:64)
at io.undertow.servlet.handlers.security.ServletSecurityConstraintHandler.handleRequest(ServletSecurityConstraintHandler.java:56)
at io.undertow.security.handlers.AuthenticationMechanismsHandler.handleRequest(AuthenticationMechanismsHandler.java:58)
at io.undertow.servlet.handlers.security.CachedAuthenticatedSessionHandler.handleRequest(CachedAuthenticatedSessionHandler.java:72)
at io.undertow.security.handlers.NotificationReceiverHandler.handleRequest(NotificationReceiverHandler.java:50)
at io.undertow.security.handlers.SecurityInitialHandler.handleRequest(SecurityInitialHandler.java:76)
at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
at org.wildfly.extension.undertow.security.jacc.JACCContextIdHandler.handleRequest(JACCContextIdHandler.java:61)
at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
at io.undertow.server.handlers.PredicateHandler.handleRequest(PredicateHandler.java:43)
at io.undertow.servlet.handlers.ServletInitialHandler.handleFirstRequest(ServletInitialHandler.java:274)
at io.undertow.servlet.handlers.ServletInitialHandler.dispatchRequest(ServletInitialHandler.java:253)
at io.undertow.servlet.handlers.ServletInitialHandler.access$000(ServletInitialHandler.java:80)
at io.undertow.servlet.handlers.ServletInitialHandler$1.handleRequest(ServletInitialHandler.java:172)
at io.undertow.server.Connectors.executeRootHandler(Connectors.java:199)
at io.undertow.server.HttpServerExchange$1.run(HttpServerExchange.java:774)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at java.lang.Thread.run(Thread.java:745)