Overlapping IPv6 Fragments

Antonios Atlasis is an independed IT security analyst who just recently joined the Centre for Strategic Cyberspace + Security Science non-profit organization. This year he released a paper called “Attacking IPv6 Implementation Using Fragmentation“. If you are interested in the security issues that arise from IP packets fragmentation then you should read it. It describes how it can be used by attackers to elude intrusion detection systems. It also includes PoC produced with Scapy tool. Eventually, one of the results of this research is the fresh CVE-2012-4444.

Worth to note is that IETF released a standard RFC number 5722 about this topic back in December 2009. On this RFC, Suresh Krishnan from the IPv6 working group, clearly states that IPv6 specification should prevent overlapping fragments. We should clearly see adoption of this RFC by the security industry in the future.

Attacks via IP packet fragmentation are not new and they were very well documented in January 1998 by Thomas Ptacek and Timothy Newsham on the landmark paper on this topic called “Insertion, Evasion, and Denial of Service: Eluding Network Intrusion Detection”. Based on this paper Dug Song released a tool called fragrouter and later fragroute which implemented the techniques described in that paper. But that’s a different story and It’s my intention to write more about this topic in a near future because it’s still being discussed today.

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