It's been almost two years since Michael Lynn first demonstrated a reliable code execution exploit on Cisco IOS at Black Hat 2005. Although his presentation received a lot of media coverage in the security community, very little is known about the attack and the technical details surrounding the IOS check_heaps() vulnerability.

This paper is a result of research carried out by IRM to analyse and understand the check_heaps() attack and its impact on similar embedded devices. Furthermore, it also helps developers understand security-specific issues in embedded environments and developing mitigation strategies for similar vulnerabilities.

The paper primarily focuses on the techniques developed for bypassing the check_heaps() process, which has traditionally prevented reliable exploitation of memory-based overflows on the IOS platform. Using inbuilt IOS commands, memory dumps and open source tools IRM was able to recreate the vulnerability in a lab environment.


The material is divided in three sections, which cover the ICMPv6 source-link attack vector, IOS Operating System internals, and finally the analysis of the attack itself.

Download the article in PDF format here.