Troubleshooting Guide: SQL Server Error 4627 – “Cannot Grant Permission”

Why This Error Happens

Error 4627 occurs when a principal (user or role) attempts to be granted a permission that is either invalid for the target securable or restricted by the database’s compatibility level. This frequently happens after an in-place upgrade to SQL Server 2025, where legacy permission grants or deprecated system objects no longer align with the new security model. It can also surface due to a corrupted or outdated system catalog view, or because the executing login lacks the CONTROL or ALTER ANY USER permission required to modify grants on the target object.

Step-by-Step Resolution Guide

Step 1: Verify the Database Compatibility Level

• Open SQL Server Management Studio (SSMS) and connect to the instance.
• Run the following query to check the current compatibility level:

  SELECT name, compatibility_level FROM sys.databases WHERE name = 'YourDatabaseName';

• If the level is below 160 (SQL Server 2022) or 170 (SQL Server 2025), update it:

  ALTER DATABASE YourDatabaseName SET COMPATIBILITY_LEVEL = 170;

Step 2: Confirm the Permission Is Valid for the Securable

• Cross-reference the permission name against sys.fn_builtin_permissions(DEFAULT) to ensure it still applies in SQL Server 2025:

  SELECT * FROM sys.fn_builtin_permissions(DEFAULT) WHERE permission_name = 'YourPermission';

• Some permissions tied to deprecated features (e.g., SQL Server Agent Proxy roles) were removed or renamed; adjust your GRANT statement accordingly.

Step 3: Check Executing Login’s Administrative Rights

• Ensure the account running the GRANT statement has CONTROL SERVER or ALTER ANY USER permission:

  SELECT * FROM sys.fn_my_permissions(NULL, 'SERVER');

• If missing, escalate temporarily via a sysadmin account to execute the grant, then review least-privilege policy afterward.

Step 4: Repair Corrupted Security Catalog (If Applicable)

• Run DBCC CHECKCATALOG('YourDatabaseName') to detect metadata corruption.
• If errors are returned, restore the database from a known-good backup or run DBCC CHECKDB with the REPAIR_ALLOW_DATA_LOSS option as a last resort (ensure you have a full backup first).

Step 5: Reapply the Grant Statement

• Using a sysadmin-level connection, reissue the exact GRANT statement that failed.
• Example:

  GRANT SELECT ON OBJECT::dbo.YourTable TO [YourUser];

Alternative or Verification Steps

• Verify the fix by querying sys.database_permissions to confirm the grant was successfully applied to the target principal.
• If the issue persists, use the SQL Server 2025 Permissions Troubleshooter (new diagnostic tool in SSMS 21+) under Tools > Diagnostics > Permission Analyzer to pinpoint the exact securable conflict.