The automatic update feature in Google Talk allows remote attackers to cause a denial of service (CPU and memory consumption) by poisoning a target's DNS cache and causing a large update file to be sent, which consumes large amounts of CPU and memory during the signature verification, aka BenjiBug.
Google Talk before 1.0.0.76, with email notification enabled, allows remote attackers to cause a denial of service (connection reset) via email with a blank sender.