Error 18452 appears when SQL Server cannot validate the login because the connection is not associated with a trusted security context.
SQL Server Error 18452 (“Login failed for user ''. The user is not associated with a trusted SQL Server connection.”) means the server received Windows credentials it cannot verify. Enable Mixed Mode or use a valid Windows login, then restart the SQL Server service to clear the error.
Login failed for user ''. The user is not associated with a trusted SQL Server connection. (Error 18452)
Error 18452 happens at login time when SQL Server receives a Windows security token it cannot validate. The engine rejects the session and returns “Login failed for user ''. The user is not associated with a trusted SQL Server connection.”
This authentication failure blocks application traffic, scheduled jobs, and interactive logins.
Resolving it quickly restores database availability and prevents cascading outages.
SQL Server throws 18452 when Windows Authentication is attempted but the login originates from an untrusted domain or when the server is configured for Mixed Mode yet receives mismatched credentials. Network hops that strip Kerberos tickets or missing SPNs also trigger the error.
First, confirm whether the client should use Windows or SQL authentication.
If Windows Auth is intended, join the server to the same domain, create a corresponding login, and verify Kerberos delegation. If SQL Auth is intended, enable Mixed Mode and connect with a SQL login.
Cross-domain logins fail because the domains lack a trust; create or restore the trust or switch to SQL authentication. After a server migration, SPNs may be missing; register them with setspn -S MSSQLSvc/FQDN:port ServiceAccount.
For local connections, disable “Force Kerberos” in the client network configuration.
Standardize on one authentication model per environment, enforce domain trust validation during server provisioning, and automate SPN registration. Monitor the SQL error log for 18452 events and alert the DBA team immediately.
Error 18456 signals generic login failure with state codes. Error 17806 indicates SSPI handshake problems.
Both are often cleared by the same authentication and SPN fixes used for 18452.
Clients using SQL logins receive 18452 because the server refuses non-Windows credentials.
The Windows token cannot be validated across domains, so SQL Server treats the user as untrusted.
A multi-hop connection drops the Kerberos ticket, leaving SQL Server unable to authenticate the user.
Without a correct SPN, the SSPI handshake fails and SQL Server raises 18452.
Changing to Mixed Mode requires a SQL service restart; otherwise, the new setting is not active.
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Mixed Mode adds SQL logins, which rely on stored password hashes. Mitigate risk by enforcing strong passwords, limited roles, and auditing.
Yes. SQL Server caches the LoginMode value. Restarting applies the new mode and clears authentication cache.
Galaxy’s AI copilot highlights authentication failures in real time and surfaces error 18452 in the query history sidebar, helping engineers fix problems faster.
When SQL Server cannot map the Windows token, it logs an empty string for the user, signalling no valid login was supplied.
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