OSEC

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[SST]ServU MDTM command remote buffero verflow adv

From: icbm (icbm0x557.net)
Date: Sat Jan 24 2004 - 01:49:24 CST


Serv-U Ftp Server Long Filename Stack Overflow Vunlnerablity
 
Application: Serv-U
 
Affected Versions: All versions prior 4.2 (include 4.1.0.11)
 
Vendor: RhinoSoft (http://www.rhinosoft.com
                       http://www.serv-u.com)
 
URL: http://www.0x557.org/release/servu.txt

Vunlnerablity:
 
  An internal memory buffer may be overrun while handling "site chmod" command
with a filename containg excessive data. This condition may be exploited by
attackers to ultimately execute instructions with the priviledges of the serv-u
process, typically administator or system.
 
Details:
  
  While exectuing chmod on a nonexistent file, serv-u will call sprintf to
construct response string. And the code is like
  sprintf(dst, "%s: No such file or directory.", filename);
 
  The length of dst buffer is only 256 bytes.If a long filename was sent,
serv-u will crash.
 
  A writable directory is needed to exploit this vulerablity.By overwriting SEH,
we have created proof-of-concept exploit successfully on win2k/xp.
 
Solution:
 
  Upgrade to servu 5.0.
 
Credits:
 
  kkqq <kkqq0x557.org> has indenpendently discovered this vulerablity.
  All members of SST (http://www.0x557.org).
  lgx and eyas.
  Rob Beckers for indentifing and fixing this vulerablity.
 
About SST:
 
  Do we really exist?




        icbm
        icbm0x557.net
          2004-01-24