When I go to "Manage Servers in Farm" from Central Admin, I see a red alert that says "Upgrade Required" against web front end. When I run the stsadm command
stsadm.exe -o localupgradestatus
, I get the following output:
<objects> <object> <name>SharePoint_Config</name> <type>Microsoft.SharePoint.Administration.SPConfigurationDatabase</type> <level>0</level> <status>Needs Upgrade</status> </object> </objects>  content database(s) encountered.  content database(s) still need upgrade or cannot be upgraded.  site collection(s) are contained in the content databases.  site collection(s) still need upgrade.  other objects encountered,  of them still need upgrade or cannot be upgraded.
I Tried psconfig command :
psconfig -cmd upgrade -inplace b2b -wait
and the result was:
SharePoint Products Configuration Wizard version 15.0.4569.1503. Copyright (C) M icrosoft Corporation 2012. All rights reserved.
The upgradebootstrap command is invalid or a failure has been encountered. An error has occurred while validating the configuration settings. An exception of type System.Data.SqlClient.SqlException was thrown. Additional exception in formation: The EXECUTE permission was denied on the object 'proc_GetProductVersions', database 'SharePoint_Config', schema 'dbo'.
Can anyone tell me what I need to do?