Spring Security LDAP Server returns 401 Unauthorized

Question

I'm trying to connect to an online LDAP test server using LdapUserDetailsManager (spring-security-ldap version 6).

Link of the online LDAP server is (for more information): https://www.forumsys.com/2022/05/10/online-ldap-test-server/

LDAP Server Information:

• Server: ldap.forumsys.com
• Port: 389
• Bind DN: cn=read-only-admin,dc=example,dc=com
• Bind Password: password
• All user passwords are password.
• ou=mathematicians,dc=example,dc=com
• uid: riemann or euler or euclid ...

This is my config class:

@Configuration
public class ProjectConfig {

    @Bean
    public UserDetailsService userDetailsService() {
        var cs = new DefaultSpringSecurityContextSource("ldap://ldap.forumsys.com:389/dc=example,dc=com");
        cs.setUserDn("cn=read-only-admin,dc=example,dc=com");
        cs.setPassword("password");
        cs.afterPropertiesSet()

        LdapUserDetailsManager manager = new LdapUserDetailsManager(cs);
        manager.setUsernameMapper(
                new DefaultLdapUsernameToDnMapper("dc=example,dc=com", "uid"));
        manager.setGroupSearchBase("ou=mathematicians");
        return manager;
    }

    @Bean
    public PasswordEncoder passwordEncoder() {
        return NoOpPasswordEncoder.getInstance();
    }

}

The cURL request:

curl -u "riemann:password" -X GET http://localhost:8080

But I got 401 Unauthorized.

Part of the debug log:

AuthenticationSource not set - using default implementation
Using LDAP pooling.
Trying provider Urls: ldap://ldap.forumsys.com:389/dc=example,dc=com
AuthenticationSource not set - using default implementation
Property 'userDn' not set - anonymous context will be used for read-write operations
Not using LDAP pooling
...
...
Got Ldap context on server 'ldap://ldap.forumsys.com:389/dc=example,dc=com'
Loading user 'riemann' with DN 'uid=riemann,dc=example,dc=com'
Got Ldap context on server 'ldap://ldap.forumsys.com:389/dc=example,dc=com'
Failed to find user 'riemann'
Failed to process authentication request

org.springframework.security.authentication.BadCredentialsException: Bad credentials

What's wrong with this code segment?