EnGarde: ‘stunnel’ format string vulnerability

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Author: JT Smith

En Garde: “There is a format string vulnerability in stunnel which may allow an attacker to exploit a victim by impersonating a mail server.”



+------------------------------------------------------------------------+

| EnGarde Secure Linux Security Advisory               December 27, 2001 |

|  http://www.engardelinux.org/ ESA-20011227-01 |

|                                                                        |

| Package:  stunnel                                                      |

| Summary:  There is a format string vulnerability in stunnel.           |

+------------------------------------------------------------------------+



  EnGarde Secure Linux is a secure distribution of Linux that features

  improved access control, host and network intrusion detection, Web

  based secure remote management, complete e-commerce using AllCommerce,

  and integrated open source security tools.





OVERVIEW

--------

  There is a format string vulnerability in stunnel which may allow an

  attacker to exploit a victim by impersonating a mail server.





DETAIL

------

  There are a couple of instances in stunnel where a format is not passed

  to a printf-like function, leading to your classic format string

  vulnerability.  It is not know weather or not it is exploitable at this

  time but all users are recommended to upgrade in any event.



  This vulnerability was disclosed on December 18 by Matthias Lange on

  the stunnel-users mailing list.  The original message may be found here:



     http://marc.theaimsgroup.com/?l=stunnel-users&m=100868569203440&w=3



All users should upgrade to the most recent version, as outlined in





SOLUTION

--------

  All users should upgrade to the most recent version as outlined in

  this advisory.  All updates may be found at:



     ftp://ftp.engardelinux.org/pub/engarde/stable/updates/http://ftp.engardelinux.org/pub/engarde/stable/updates/



Before upgrading the package, the machine must either:



    a) be booted into a "standard" kernel; or

    b) have LIDS disabled.



  To disable LIDS, execute the command:



    # /sbin/lidsadm -S -- -LIDS_GLOBAL



  To install the updated package, execute the command:



    # rpm -Uvh 



You must now update the LIDS configuration by executing the command:



    # /usr/sbin/config_lids.pl



  To re-enable LIDS (if it was disabled), execute the command:



    # /sbin/lidsadm -S -- +LIDS_GLOBAL



  To verify the signatures of the updated packages, execute the command:



    # rpm -Kv 





UPDATED PACKAGES

----------------

  These updated packages are for EnGarde Secure Linux 1.0.1 (Finestra).



  Source Packages:



    SRPMS/stunnel-3.22-1.0.4.src.rpm

      MD5 Sum:  e408662d6fc54f3979642c9e8c110ba4



  Binary Packages:



    i386/stunnel-3.22-1.0.4.i386.rpm

      MD5 Sum:  482ff9210541d73b114404ccb9732cf0



    i686/stunnel-3.22-1.0.4.i686.rpm

      MD5 Sum:  afad91053b8d482e36e85251fab06755





REFERENCES

----------



  Guardian Digital's public key:

     http://ftp.engardelinux.org/pub/engarde/ENGARDE-GPG-KEY



Credit for the discovery of this bug goes to:

    Matthias Lange ml@netuse.de>



stunnel's Official Web Site:

     http://stunnel.mirt.net/



Security Contact:    security@guardiandigital.com

EnGarde Advisories:   http://www.engardelinux.org/advisories.html



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$Id: ESA-2001122701-stunnel,v 1.2 2001/12/27 16:02:00 rwm Exp $

--------------------------------------------------------------------------

Author: Ryan W. Maple, ryan@guardiandigital.com>

Copyright 2001, Guardian Digital, Inc.

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