Today Cisco released an advisory regarding IOS Head-based Overflow Vulnerability in System Timers. It can be found here. Some users wrote to us asking about rush to upgrade the routers. In the words of one of our handlers, a brief explanation is that "this is related to the ipv6 vulnerability that cisco released patches for midyear AND the mike lynn black hat breifing which exploited that vulnerability and a timer vulnerability."
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Handler on Duty: Pedro Bueno (pbueno //%// isc. sans. org)