Problem

Users are unable to log in. Nothing has changed in Confluence side.

The following appears in the atlassian.confluence.log:

2017-10-25 14:13:07,009 ERROR [scheduler_Worker-3] [atlassian.crowd.directory.DbCachingDirectoryPoller] pollChanges Error occurred while refreshing the cache for directory [ 31064065 ].
com.atlassian.crowd.exception.OperationFailedException: Error looking up attributes for highestCommittedUSN
	at com.atlassian.crowd.directory.MicrosoftActiveDirectory.fetchHighestCommittedUSN(MicrosoftActiveDirectory.java:847)

...

Caused by: org.springframework.ldap.AuthenticationException: [LDAP: error code 49 - 80090308: LdapErr: DSID-0C09042F, comment: AcceptSecurityContext error, data 52e, v2580 ]; nested exception is javax.naming.AuthenticationException: [LDAP: error code 49 - 80090308: LdapErr: DSID-0C09042F, comment: AcceptSecurityContext error, data 52e, v2580 ]

Cause

LDAP Error 49 data 52e means that the credentials of the user configured to bind LDAP directory with Confluence are incorrect, as described here: https://confluence.atlassian.com/kb/common-user-management-errors-820119309.html#CommonUserManagementErrors-ActiveDirectoryError49

This can happen when that user is either removed or has its password changed from LDAP side.

Resolution 1

Follow the steps outlined at Restore Passwords To Recover Admin User Rights. By doing so, you'll be able to access the User Directory settings and change the "Username" field with a valid admin user or change the "Password" field with the new password, allowing Confluence to connect to LDAP.

Resolution 2

Alternatively, you can run the following query against your database to find out which one is the admin account that Confluence uses to connect to the LDAP:

SELECT * FROM cwd_directory_attribute WHERE attribute_name = 'ldap.userdn'; 

Note: The query may return multiple results in case you have more than one User Directory in your Confluence instance.

Re-adding the user back to the LDAP with the same password should resolve the issue.