In Wireshark 2.6.0 to 2.6.5 and 2.4.0 to 2.4.11, the ISAKMP dissector could crash. This was addressed in epan/dissectors/packet-isakmp.c by properly handling the case of a missing decryption data block.
Created wireshark tracking bugs for this issue:
Affects: fedora-all [bug 1667593]
Function dissect_transform() in packet-isakmp.c has a NULL pointer dereference flaw. The `decr` parameter may be NULL, but it is dereferenced without any check, thus leading to a crash.