iDEFENSE Security Advisory 09.01.05: Novell NetMail IMAPD Command Continuation Request Heap Overflow

From: iDEFENSE Labs (
Date: 09/01/05

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    Novell NetMail IMAPD Command Continuation Request Heap Overflow

    iDEFENSE Security Advisory 09.01.05
    September 1, 2005


    Novell NetMail is an e-mail and calendaring system that is based on
    Internet-standard messaging and security protocols. More information
    about Novell NetMail is available from:


    Remote exploitation of a heap overflow vulnerability in Novell Inc.'s
    NetMail IMAP daemon allows unauthenticated attackers to execute
    arbitrary code with the privileges of the underlying user.

    The problem specifically exists in the handling of command continuation
    requests as the user-specified size value is used directly as the
    argument to a custom memory allocation wrapper (MMalloc()):

    00402CA2 lea ecx, [ebx+1] ; ebx is attacker controlled
    00402CA5 push ecx
    00402CA6 call MMmalloc

    The MMalloc() routine performs minimal mathematical operations to the
    supplied value before allocating memory. An attacker can specify a
    malicious number that will result in an integer overflow and cause a
    small memory chunk to be allocated. The original and larger supplied
    value will be later used in an inline memcpy():

        00402D6E rep movsd ; destination is attacker allocated
        00402D70 mov ecx, edx
        00402D72 and ecx, 3
        00402D75 rep movsb

    This instruction sequence will copy attacker-supplied data beyond the
    brims of the allocated heap chunk and arbitrarily overwrite the heap.
    Too large a payload will cause an access violation as it writes off the
    end of the heap. If the supplied data is large enough, it will corrupt
    the heap and eventually result in a classic arbitrary DWORD overwrite
    in NTDLL during subsequent heap manipulation:

        77FCC2C0 mov [ecx], eax
        77FCC2C2 mov [eax+4], ecx

    By overwriting the address of a soon to be called function, the attacker
    can redirect CPU flow and eventually execute arbitrary code.


    Successful exploitation of the described vulnerability allows
    unauthenticated remote attackers to execute arbitrary code with the
    privileges of the underlying user, normally NetMailService.


    iDEFENSE has confirmed the existence of the vulnerability in the latest
    version of Novell NetMail, version 3.5.2. It is suspected that earlier
    versions of NetMail are also affected.


    Employ firewalls, access control lists or other TCP/UDP restriction
    mechanisms to limit access to systems and services.


    The following vendor advisory has been released to address this


    The Common Vulnerabilities and Exposures (CVE) project has assigned the
    name CAN-2005-1758 to this issue. This is a candidate for inclusion in
    the CVE list (, which standardizes names for
    security problems.


    04/25/2005 Initial vendor notification
    04/25/2005 Initial vendor response
    09/01/2005 Public disclosure


    This vulnerability was discovered by Pedram Amini, OpenRCE

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    Copyright (c) 2005 iDEFENSE, Inc.

    Permission is granted for the redistribution of this alert
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    email for permission.

    Disclaimer: The information in the advisory is believed to be accurate
    at the time of publishing based on currently available information. Use
    of the information constitutes acceptance for use in an AS IS condition.
    There are no warranties with regard to this information. Neither the
    author nor the publisher accepts any liability for any direct, indirect,
    or consequential loss or damage arising from use of, or reliance on,
    this information.

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