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Mohamed4053 avatar image
Mohamed4053 asked

Login failed for user ''

Hello All, Good day. I am new to SQL SERVER. I have checked the my sql server error log and i am seeing lots of error message from many IP address as mentioned Below. I have placed sample error log detail Below. *Login failed for user ''. Reason: An attempt to login using SQL authentication failed. Server is configured for Windows authentication only. [CLIENT: 192.168.XX.XXX] Error: 18456, Severity: 14, State: 58. Login failed for user ''. Reason: An attempt to login using SQL authentication failed. Server is configured for Windows authentication only. [CLIENT: 192.168.XX.XXX]* **Note:-** I have checked the authentication, It's a mixed mode authentication... I don't have much information about application details. Please let me know if you have any idea what could be the reason for issue or any one faced and resolved this issue.
sql-servererror-log
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KenJ avatar image KenJ commented ·
Perhaps the server used to be windows only then was changed to mixed mode and not restarted? Is your sql login enabled and allowed to connect? Are you connecting with the empty string as the sql username or is that just to clean up the question?
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Mohamed4053 avatar image Mohamed4053 commented ·
1. Last week we restarted that machine, after that also we are seeing this error in Error log. 2. Yes i am able to connect that sql server through sql server authentication mode. 3. I am not sure if any of the applications are trying to connect the server with empty string.
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KenJ avatar image KenJ commented ·
can you login to the client machine [192.168.xx.xxx] and connect with the sql login from there? I'm with Grant on the AD portion except for the part in the error message about the server security configuration and error sate 58
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Grant Fritchey avatar image Grant Fritchey ♦♦ commented ·
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Grant Fritchey avatar image
Grant Fritchey answered
Usually when I see this, it's someone attempting to connect from an Active Directory account that doesn't have access to the server. So, something has changed inside the database, your SQL Server instance, or in Active Directory. Check each and every one of these thoroughly. That's where the error is.
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Mohamed4053 avatar image Mohamed4053 commented ·
Hi Grand and Ken, Thanks for spending your valuable timing for my post. As of now i didn't hear any issues from any user. While checking the error log i found those errors and i want to clarify with you Guys. I am guessing that applications(Which is generating the error) are not used by anyone. I don't want to dig more on this, Because i need to explore in sql answer.
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Blackhawk-17 avatar image
Blackhawk-17 answered
This is generally the dreaded [double hp][1] - AD credentials being presented to an intermediate process that can't pass them on to SQL Server. Check for SPNs & Kerberos and/or impersonation permissions in the middle tier and check this [article][2]. [1]: http://blogs.msdn.com/b/sql-bi-sap-cloud-crm_all_in_one_place/archive/2012/08/12/checklist-for-double-hop-issues-iis-and-sql-server.aspx [2]: https://sqlbadboy.wordpress.com/2013/10/11/the-kerberos-double-hop-problem/
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