SharePoint Portal Server 2003 Service Pack 3 & Windows SharePoint Services Service Pack 3 available for download
Description of SharePoint Portal Server 2003 Service Pack 3
https://support.microsoft.com/?id=923644
Issues that are fixed in SharePoint Portal Server 2003 by SharePoint Portal Server 2003 Service Pack 3
https://support.microsoft.com/?id=938795
SharePoint SP3 Download Site
Description of Windows SharePoint Services Service Pack 3
https://support.microsoft.com/?id=923643
Issues that are fixed in Windows SharePoint Services by Windows SharePoint Services Service Pack 3
https://support.microsoft.com/?id=938793
Windows SharePoint Services SP3 Download Site