INFORMATION BULLETIN

E-17: FTP Daemon Vulnerabilities

April 14, 1994 1130 PDT


PROBLEM:   Vulnerabilities in several implementations of the FTP daemon.
PLATFORM:  Unix systems with the following implementations of the FTP
             daemon: DECWRL ftpd versions before 5.93, wuarchive ftpd
             versions 2.0-2.3, and BSDI ftpd version 1.1. prior to patch 5.
DAMAGE:    Anyone (remote or local) can gain root access on a host
             running a vulnerable daemon.
SOLUTION:  Upgrade to a secure version of the FTP daemon.

VULNERABILITY   Details of these vulnerabilities are being actively discussed
ASSESSMENT:     on several Internet mailing lists.  CIAC urges affected sites
               to upgrade immediately.

Critical Information about FTP Daemon Vulnerabilities

CIAC has received information concerning the existence of two vulnerabilities in FTP daemons derived from the DECWRL ftpd source code. The following FTP daemons are known to be vulnerable:

  
   - DECWRL ftpd versions before 5.93
   - wuarchive ftpd versions 2.0-2.3
   - BSDI ftpd version 1.1 prior to patch 5

The first vulnerability involves the SITE EXEC command feature of these FTP daemons. It only affects those daemons in which the SITE EXEC functions have been explicitly activated; they are not enabled by default. The vulnerability allows any user, remote or local, to execute commands as root on the system running the FTP daemon. The second vulnerability is the result of a race condition in the daemon. It allows the creation of setuid root files on the FTP server, permitting unauthorized access to the system.

There is no known workaround to remove both vulnerabilities; therefore, CIAC strongly advises affected sites to upgrade to one of the versions of the daemon listed below. If an upgrade cannot be completed in a timely manner, FTP service should be disabled by commenting out the ftp configuration line in /etc/inetd.conf and restarting inetd. Disabling only anonymous FTP does not remove the vulnerabilities.

Upgrade Information

Version 2.4 of wuarchive ftpd is available via anonymous FTP from wuarchive.wustl.edu in the directory /packages/wuarchive-ftpd. A patch to upgrade from version 2.3 to 2.4 is also available:

                        BSD        SVR4         
   File               Checksum   Checksum   MD5 Digital Signature
   -----------------  ---------  ---------  --------------------------------
   wu-ftpd-2.4.tar.Z  38213 181  20337 362  cdcb237b71082fa23706429134d8c32e
   patch_2.3-2.4.Z    09291   8  51092  16  5558a04d9da7cdb1113b158aff89be8f

Version 5.93 of DECWRL ftpd is available via anonymous FTP from gatekeeper.dec.com in the directory /pub/misc/vixie:

                         BSD        SVR4         
   File               Checksum   Checksum   MD5 Digital Signature
   -----------------  ---------  ---------  --------------------------------
   ftpd.tar.gz        38443 60   1710 119   ae624eb607b4ee90e318b857e6573500

For BSDI systems, patch 005 should be applied to version 1.1 of the BSD/386 software. The patch file is available via anonymous FTP from ftp.bsdi.com in the directory /bsdi/patches-1.1:

   
                      BSD        SVR4         
   File               Checksum   Checksum   MD5 Digital Signature
   -----------------  ---------  ---------  --------------------------------
   BU110-005          35337 272  54935 543  1f454d4d9d3e1397d1eff0432bd383cf

CIAC wishes to thank the CERT Coordination Center for their response to this problem.

CIAC services are available to DOE, DOE Contractors, and the NIH. CIAC can be contacted at:

    Voice:          +1 925-422-8193 (7 x 24)
    FAX:            +1 925-423-8002
    STU-III:        +1 925-423-2604
    E-mail:          ciac@ciac.org
    World Wide Web:  http://www.ciac.org/
    Anonymous FTP:   ftp.ciac.org

This document was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor the University of California nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial products, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation or favoring by the United States Government or the University of California. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or the University of California, and shall not be used for advertising or product endorsement purposes.

UCRL-MI-119788
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