Your firewall has a version number null which is not supported by ASDM 6.2(5). I received this error when trying to run asdm on my asa 5505. I upgraded image and asdm trying different versions. I used many different versions of java all to no avail. In order to fix this issue you must have the same authentication for ssh and http in your AAA commands. For example, I had ssh to use TACACS but http authentication was set for LOCAL. When I changed AAA for http to TACACS the problem went away and I was able to use asdm.
Table of ContentsIntroductionVersion HistoryPossible Future
UpdatesDocuments PurposeNAT Operation in ASA 8.3+ SectionsRule Types
Network Object NATTwice NAT / Manual NATRule Types used per SectionNAT
Types used with Twice NAT / Manual NAT and Network Obje...
Table of Contents Introduction:This document describes details on how
NAT-T works. Background: ESP encrypts all critical information,
encapsulating the entire inner TCP/UDP datagram within an ESP header.
ESP is an IP protocol in the same sense that TCP an...