[NT] Halo Off-By-One Bug Can Crash Multiplayer Server

From: SecuriTeam (support_at_securiteam.com)
Date: 09/14/04

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    Date: 14 Sep 2004 15:16:10 +0200

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      Halo Off-By-One Bug Can Crash Multiplayer Server


    " <http://www.bungie.net/Games/HaloPC/> Halo for PC is a conversion of
    Bungie's Xbox classic - a first person sci-fi shooter set on a ring-shaped
    alien artifact in deep space, as you in the role of Master Chief, attempt
    to stop an alien race known as The Covenant from reaching Earth."

    A bug in the way the server handles handshakes with a connecting client
    allows the client to crash the server if a malformed packet is sent.


    Vulnerable Systems:
     * Halo: Combat Evolved, version 1.4 and prior (PC and Mac)

    Immune Systems:
     *Halo: Combat Evolved, patch version 1.5 (PC and Mac)

    Halo uses the Gamespy SDK and specifically, the handshake algorithm
    provided in this library to let players to join servers. A breakdown of
    the algorithm is given by Luigi at

    In the last stage of the handshake taking place between the server and the
    connecting client, the client is sending the last response. If this last
    response is longer than 32 bytes, it will immediately cause the Halo
    online server to crash.

    A proof of concept code that demonstrates this can be downloaded from


    The information has been provided by <mailto:aluigi@autistici.org> Luigi


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