[VulnWatch] Secunia Research: FTPServer/X Response Buffer Overflow Vulnerability

From: Carsten H. Eiram (che_at_secunia.com)
Date: 06/26/03

  • Next message: François SORIN: "[KSA-002] Multiple Vulnerabilities In Moregroupware"
    To: Full Disclosure <full-disclosure@lists.netsys.com>, VulnWatch <vulnwatch@vulnwatch.org>
    Date: 26 Jun 2003 17:00:57 +0200
    
    

    ======================================================================

                          Secunia Research 26/06/2003

            - FTPServer/X Response Buffer Overflow Vulnerability -

    ======================================================================
    Receive Secunia Security Advisories for free:
    http://www.secunia.com/secunia_security_advisories/

    ======================================================================
    Table of Contents
    1....................................................Affected Software
    2.............................................................Severity
    3.....................................Vendor's Description of Software
    4.........................................Description of Vulnerability
    5.............................................................Solution
    6...........................................................Time Table
    7..............................................................Credits
    8........................................................About Secunia
    9.........................................................Verification

    ======================================================================
    1) Affected Software

    FTPServer/X - FTP Server Control and COM Object v1.00.046.
    FTPServer/X - FTP Server Control and COM Object v1.00.045.

    Prior versions have not been tested, but may also be vulnerable.

    Used in the following products:
    Simple FTPServer Example (included with FTPServer/X)
    Mollensoft FTP Server 3.5.2 (formerly known as Hyperion)
    Hyperion FTP Server 3.0.0 (updated version downloaded 10/04/2003)

    NOTE: Any FTP server using FTPServer/X may be vulnerable.

    ======================================================================
    2) Severity

    Rating: Highly critical
    Impact: Denial of Service, System Access
    Where: From Remote

    ======================================================================
    3) Vendor's Description of Software

    "FTPServer/X makes it easy for you to put up an FTP server.
    FTPServer/X comes in both ActiveX Control and COM Object forms to
    make it easy for you to integrate it into nearly any Windows
    programming environment. When you use FTPServer/X, you have complete
    control over user access, directories, file uploads and downloads,
    deletion, etc."

    Vendor:
    Mabry Software
    http://www.mabry.com

    ======================================================================
    4) Description of Vulnerability

    A vulnerability has been identified in FTPServer/X, which can be
    exploited by malicious people to cause a DoS (Denial of Service) on a
    vulnerable FTP server or potentially compromise it.

    The vulnerability is caused due to a boundary error, when the FTP
    Server returns responses, which include user input. The problem is
    that the allocated buffer (1024 bytes) may be overflowed due to an
    insecure use of the "wsprintf()" function.

    When exploiting the vulnerability, the return address as well as a
    pointer stored in the register "ecx" can be overwritten with
    arbitrary values.

    Before returning, the manipulated pointer is used as an argument to
    the function "InterlockedDecrement()" in "kernel32.dll", which may
    cause a vulnerable FTP server to crash.

    The FTP service needs to be restarted manually before functionality
    is restored.

    Since the return address also is overwritten, the vulnerability can
    potentially also be exploited to execute arbitrary code on a
    vulnerable system.

    The following two examples exploit the vulnerability.

    Exploit 1 (Supply between 995 and 1017 bytes to the USER command):
    telnet [victim] 21
    USER AAAA...[995-1017]...AAAA

    The FTP Server will crash when the "331 Password required for %s"
    response is returned.

    Exploit 2 (Supply a 991 to 1022 bytes long invalid command):
    telnet [victim] 21
    AAAA...[991-1022]...AAAA

    The FTP Server will crash when the response "500 '%s': command not
    understood" is returned.

    Please note that "Exploit 2" is the same issue as the one reported
    by Moran Zavdi at the beginning of April in Hyperion FTP Server
    3.0.0. However, this was erroneously thought to be fixed in an
    updated version of Hyperion FTP Server 3.0.0.

    ======================================================================
    5) Solution

    Mabry Software has fixed the vulnerability in FTPServer/X version
    1.00.047.

    Mollensoft has issued Mollensoft FTP Server version 3.5.3, which uses
    the latest version of FTPServer/X.

    If your FTP server uses the FTPServer/X component (look for
    "FTPServX.dll" / "FTPServX.ocx"), check to see if an updated version
    of the product has been made available.

    ======================================================================
    6) Time Table

    10/04/2003 - Vulnerability discovered in Hyperion FTP Server.
    11/04/2003 - Vendor notified (support@mollensoft.com).
    22/04/2003 - Vendor contacted again requesting acknowledgment.
    22/04/2003 - Vendor confirms vulnerability and states that it will
    be fixed in version 3.5.2.
    26/04/2003 - Vendor releases version 3.5.2.
    28/04/2003 - Vulnerability still present in latest version. Vendor
    notified (support@mollensoft.com).
    29/04/2003 - Mabry Software notified (techsupport@mabry.com) since the
    vulnerability may be caused by a boundary error in FTPServer/X used
    in Hyperion/Mollensoft FTP Server.
    09/05/2003 - Vulnerability conclusively identified in FTPServer/X.
    09/05/2003 - Vendor notified again (techsupport@mabry.com).
    09/05/2003 - Vendor confirms vulnerability.
    03/06/2003 - Vendor releases updated version (1.00.046).
    04/06/2003 - Vulnerability still present in latest version. Vendor
    informed (techsupport@mabry.com).
    12/06/2003 - Vendor provides source code and asks for help in
    identifying the problem.
    16/06/2003 - Problem identified.
    17/06/2003 - Mabry Software releases updated version (1.00.047).
    22/06/2003 - Mollensoft releases updated version (3.5.3).
    24/06/2003 - Public disclosure.

    ======================================================================
    7) Credits

    Discovered by Carsten H. Eiram, Secunia Research.

    ======================================================================
    8) About Secunia

    Secunia collects, validates, assesses and writes advisories regarding
    all the latest software vulnerabilities disclosed to the public. These
    advisories are gathered in a publicly available database at the
    Secunia website:

    http://www.secunia.com/

    Secunia offers services to our customers enabling them to receive all
    relevant vulnerability information to their specific system
    configuration.

    Secunia offers a FREE mailing list called Secunia Security Advisories:

    http://www.secunia.com/secunia_security_advisories/

    ======================================================================
    9) Verification

    Please verify this advisory by visiting the Secunia website:
    http://www.secunia.com/secunia_research/2003-3/

    ======================================================================


  • Next message: François SORIN: "[KSA-002] Multiple Vulnerabilities In Moregroupware"

    Relevant Pages