December 21, 2005
Hat-Squad Advisory: Remote Heap Corruption Vulnerability in Interaction SIP Proxy

Hat-Squad Advisory: Remote Heap Corruption Vulnerability in Interaction SIP Proxy

Product: Interaction SIP Proxy
Vendor: Interactive Intelligence Inc. (

Systems Affected:

Vonexus Enterprise Interaction Center
Interaction SipProxy 3.0.010

Release Date: 12/21/2005

Vendor Status:

Informed on 12/11/2005
Initial response on 12/12/2005
Patch released on 12/18/2005


Interaction SIP Proxy is Microsoft Windows-based software that provides basic SIP proxy and registrar functionality as defined in the IETF SIP-oriented RFC 3261. The Interaction SIP Proxy routes incoming SIP messages based on configurable dial plan and server plans, with simplified administration via Web interface.


Hat-Squad security team has discovered a remote heap overflow in Interaction SIP Proxy. The vulnerability allows a remote attacker to overwrite heap memory and cause a a severe denial-of-service condition on system. Exploitation of this vulnerability for code execution requires a magic sequence of pre-allocations, data and size.

Technical Details:

The code in i3sipmsg.dll is responsible for handling SIP requests. The vulnerability is triggered by sending 2900 bytes of space (0x20) or TAB (0x9) characters as SIP version in a REGISTER request line. This will cause a heap overflow in SIPParser function.

A Proof of concept for this vulnerability is available at


This Vulnerability has been Discovered By Behrang Fouladi (behrang hat-squad com)


Persia, Hamid, Hesam geek, Nima, Brett Moore, class101 and Babak


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