Tried, Tested and Proven

Security Advisory 07-008 – Denial of service due to format string vulnerability in DCC file transfer

Vulnerability discovery and development:

Portcullis Security Testing Services

Credit for Discovery:

Nico Leidecker of Portcullis Computer Security Ltd discovered this vulnerability. Further research was then carried out.

Affected Systems:

Version 0.3.151 was tested to be vulnerable.


HydraIRC is an IRC client supporting DCC file transfers. The client is prone to a format string vulnerability as it passes user input to a function expecting a format string. This only occurs, when the DCC file transfer negotiation fails.


By sending a special crafted DCC file transfer request to the victim, an attacker is then able to conduct a Denial of Service attack against them.


Proof of concept exploit code is available.

Vendor Status:

The vendor has been informed and the vulnerability has been fixed.


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