I needed to scan a new Windows 7 reference build to check which security updates are required to bring the machine up-to-date. WSUS gave me this data but not in a nice spreadsheet.
Copy the CAB file to the MBSA cache folder: C:\Users\%username%\AppData\Local\Microsoft\MBSA\Cache
After some mucking and reading the FAQ, I got the correct syntax:
mbsacli /target xx.xx.xx.xx /u xxxxxx /p xxxxxx /offline /catalog D:\wsusscn2.cab