3Com® HomeConnect® Cable Modem Denial of Service

From: Alex S. Harasic (aharasicat_private)
Date: Wed Sep 26 2001 - 08:19:19 PDT

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    INFO:
    ======================================================
    object
    class Failure to Handle Exceptional Conditions
    
    remote Yes
    local No
    
    vulnerable:	3Com® HomeConnect® Cable Modem External with USB (#3CR29223 --
    DISCONTINUED)
    Not Tested:	(#3CR29223-A   -- DISCONTINUED)
    
    
    DISCUSSION:
    ======================================================
    HomeConnect is and External Cable modem manufactured by 3Com, and
    distributed by numerous Cable providers.
    
    A problem has been discovered in the cablemodem firmware that could make it
    possible for remote users to deny service to legitimate users of this
    network hardware.
    
    This hardware has port 80/TCP wide open for the entire network, letting any
    user on the internet to access the homepage that it has in it by default.
    The problem occurs when a user reaches this page, and making a request of a
    file (Existing or not) of more than 100 Characters. This will cause the
    modem to Reset in the best case.
    
    EXPLOIT:
    =======================================================
    http://target3comcablemodem/>  (That is 100
    characters)
    
    
    SOLUTION:
    ========================================================
    As a workaround for this issue, users can filter port 80 of the Cablemodem
    Or else, since this modem is discontinued (they no longer make it) you
    should just call
    your ISP, tell them about the problem and ask to replace the cablemodem for
    a newer one.
    
    
    
    
    Alex S. Harasic
    aharasicat_private
    



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