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CERT® Advisory CA-1997-16 ftpd Signal Handling VulnerabilityOriginal issue date: May 29, 1997Last revised: December 5, 1997 Added vendor information for NCR Corporation to the Updates section. A complete revision history is at the end of this file. The text of this advisory was originally released by AUSCERT as AA-97.03 ftpd Signal Handling Vulnerability on January 29, 1997, and updated on April 18, 1997. To give this document wider distribution, we are reprinting the updated AUSCERT advisory here with their permission. Only the contact information at the end has changed: AUSCERT contact information has been replaced with CERT/CC contact information. Although the text of the AUSCERT advisory has not changed, additional vendor information has been added immediately after the AUSCERT text. We will update this advisory as we receive additional information. Look for it in an "Updates" section at the end of the advisory. AUSCERT has received information that there is a vulnerability in some versions of ftpd distributed and installed under various Unix platforms. This vulnerability may allow regular and anonymous ftp users to read or write to arbitrary files with root privileges. The vulnerabilities in ftpd affect various third party and vendor versions of ftpd. AUSCERT recommends that sites take the steps outlined in section 3 as soon as possible. This advisory will be updated as more information becomes available. 1. DescriptionAUSCERT has received information concerning a vulnerability in some vendor and third party versions of the Internet File Transfer Protocol server, ftpd(8).This vulnerability is caused by a signal handling routine increasing process privileges to root, while still continuing to catch other signals. This introduces a race condition which may allow regular, as well as anonymous ftp, users to access files with root privileges. Depending on the configuration of the ftpd server, this may allow intruders to read or write to arbitrary files on the server. This attack requires an intruder to be able to make a network connection to a vulnerable ftpd server. Sites should be aware that the ftp services are often installed by default. Sites can check whether they are allowing ftp services by checking, for example, /etc/inetd.conf: # grep -i '^ftp' /etc/inetd.conf
Note that on some systems the inetd configuration file may have a different
name or be in a different location.
/etc/inetd.conf. If your site is offering ftp services, you may be able to determine the version of ftpd by checking the notice when first connecting. The vulnerability status of specific vendor and third party ftpd servers
can be found in Section 3.
2. ImpactRegular and anonymous users may be able to access arbitrary files with root privileges. Depending on the configuration, this may allow anonymous, as well as regular, users to read or write to arbitrary files on the server with root privileges.3. Workarounds/SolutionAUSCERT recommends that sites prevent the possible exploitation of this vulnerability by immediately applying vendor patches if they are available. Specific vendor information regarding this vulnerability is given in Section 3.1.If the ftpd supplied by your vendor is vulnerable and no patches are available, sites may wish to install a third party ftpd which does not contain the vulnerability described in this advisory (Section 3.2). 3.1 Vendor patchesThe following vendors have provided information concerning the vulnerability status of their ftpd distribution.Detailed information has been appended in Appendix A. If your vendor is not listed below, you should contact your vendor directly. Berkeley Software Design, Inc.
3.2 Third party ftpd distributionsAUSCERT has received information that the following third party ftpd distributions do not contain the signal handling vulnerability described in this advisory:wu-ftpd 2.4.2-beta-12
Sites should ensure they are using the current version of this software. Information on these distributions is contained in Appendix A. Sites should note that these third party ftpd distributions may offer some different functionality to vendor versions of ftpd. AUSCERT advises sites to read the documentation provided with the above third party ftpd distributions before installing. Appendix ABerkeley Software Design, Inc. (BSDI)BSD/OS 2.1 is vulnerable to the ftpd problem described in this advisory. Patches have been issued and may be retrieved via the patches@BSDI.COM email server or from:ftp://ftp.bsdi.com/bsdi/patches/patches-2.1/U210-033 Digital Equipment CorporationDIGITAL UNIX Versions:3.2c, 3.2de1, 3.2de2, 3.2f, 3.2g, 4.0, 4.0a, 4.0b SOLUTION: This potential security vulnerability has been resolved
This article will be updated accordingly when patch kits for DIGITAL
UNIX V3.2c, V3.2de1, V3.2de2, V3.2f become
The currently available patches may be obtained from your normal Digital
support channel or from the following
ftp://ftp.service.digital.com/patches/public/dunix
Please refer to the applicable README notes information prior to the installation of patch kits on your system. Note: The appropriate patch kit must be reinstalled following any upgrade
beginning with V3.2c
The FreeBSD ProjectThe FreeBSD Project has informed AUSCERT that the vulnerability described in this advisory has been fixed in FreeBSD-current (from January 27, 1997), and will be fixed in the upcoming FreeBSD 2.2 release. All previous versions of FreeBSD are vulnerable.Hewlett-Packard CorporationHewlett-Packard has informed AUSCERT that the ftpd distributed with HP-UX 9.x and 10.x are vulnerable to this problem. Patches are currently in process.IBM CorporationThe version of ftpd shipped with AIX is vulnerable to the conditions described in the advisory. The following APARs will be available shortly:AIX 3.2 : APAR IX65536
To OrderAPARs may be ordered using Electronic Fix Distribution (via FixDist) or from the IBM Support Center. For more information on FixDist, reference URL:http://service.software.ibm.com/aixsupport/ or send e-mail to aixserv@austin.ibm.com
with a subject of "FixDist".
The NetBSD ProjectNetBSD (all versions) have the ftpd vulnerability described in this advisory. It has since been fixed in NetBSD-current. NetBSD have also made patches available and they can be retrieved from:ftp://ftp.netbsd.org/pub/NetBSD/misc/security/19970123-ftpd The OpenBSD ProjectOpenBSD 2.0 did have the vulnerability described in this advisory, but has since been fixed in OpenBSD 2.0-current (from January 5, 1997).Red Hat SoftwareThe signal handling code in wu-ftpd has some security problems which allows users to read all files on your system. A new version of wu-ftpd is now available for Red Hat 4.0 which Red Hat suggests installing on all of your systems. This new version uses the same fix posted to redhat-list@redhat.com by Savochkin Andrey Vladimirovich. Users of Red Hat Linux versions earlier then 4.0 should upgrade to 4.0 and then apply all available security packages.Users whose computers have direct internet connections may apply this update by using one of the following commands: Intel:
Alpha:
SPARC:
All of these packages have been signed with Red Hat's PGP key. wu-ftpd Academ beta versionThe current version of wu-ftpd (Academ beta version), wu-ftpd 2.4.2-beta-12, does not contain the vulnerability described in this advisory. Sites using earlier versions should upgrade to the current version immediately. At the time of writing, the current version can be retrieved from:ftp://ftp.academ.com/pub/wu-ftpd/private/
logdaemon DistributionThe current version of Wietse Venema's logdaemon (5.6) package contains an ftpd utility which addresses the vulnerability described in this advisory. Sites using earlier versions of this package should upgrade immediately. The current version of the logdaemon package can be retrieved from:ftp://ftp.win.tue.nl/pub/security/ ftp://ftp.auscert.org.au/pub/mirrors/ftp.win.tue.nl/logdaemon/ ftp://ftp.cert.dfn.de/pub/tools/net/logdaemon/ The MD5 checksum for Version 5.6 of the logdaemon package is: MD5 (logdaemon-5.6.tar.gz) = 5068f4214024ae56d180548b96e9f368 AUSCERT thanks David Greenman, Wietse Venema (visiting IBM T.J. Watson Research) and Stan Barber (Academ Consulting Services) for their contributions in finding solutions to this vulnerability. Thanks also to Dr Leigh Hume (Macquarie University), CERT/CC, and DFNCERT for their assistance in this matter. AUSCERT also thanks those vendors that provided feedback and patch information contained in this advisory.
UPDATESVendor Information Added by CERT/CCDigital Equipment CorporationAUG, 1997 DIGITAL UNIX Versions:3.2C, 3.2DE1, 3.2DE2, 3.2F, 3.2G, 4.0, 4.0A, 4.0B, 4.0C SOLUTION: This potential security vulnerability has been resolved
NOTE: Previously released singular ECO patches
ftp://ftp.service.digital.com/patches/public/dunix (Select the appropriate version and it's aggregate patch kit). Please refer to the applicable README notes information
Hewlett-Packard CorporationHP has covered this in our security bulletin HPSBUX9702-055, 19 February 1997. The Security Bulletin contains pointers to the patches:SOLUTION: Apply patch: PHNE_10008 for all platforms with HP-UX releases 9.X
IBM CorporationSee the appropriate release below to determine your action.AIX 3.2Apply the following fix to your system:APAR - IX65536 (PTF - U447700) To determine if you have this PTF on your system, run the following command: lslpp -lB U447700 AIX 4.1Apply the following fix to your system:APAR - IX65537 To determine if you have this APAR on your system, run the following command: instfix -ik IX65537 Or run the following command: lslpp -h bos.net.tcp.client Your version of bos.net.tcp.client should be 4.1.5.3 or later. AIX 4.2Apply the following fix to your system:APAR - IX65538 To determine if you have this APAR on your system, run the following command: instfix -ik IX65538 Or run the following command: lslpp -h bos.net.tcp.client Your version of bos.net.tcp.client should be 4.2.1.0 or later. To OrderAPARs may be ordered using Electronic Fix Distribution (via FixDist) or from the IBM Support Center. For more information on FixDist, reference URL:http://service.software.ibm.com/aixsupport/ or send e-mail to aixserv@austin.ibm.com
with a subject of "FixDist".
NCR CorporationNCR is delivering a set of operating system dependent patches which contain an update for this problem. Accompanying each patch is a README file which discusses the general purpose of the patch and describes how to apply it to your system.Recommended solution: Apply one of the following patches depending on the revision of the inet package installed on your system. To check its version execute: pkginfo -x inet
Silicon Graphics Inc.The ftpd program (/usr/etc/ftpd) is installed on all IRIX systems by default.Patch information for this vulnerability is available in SGI"s Security Advisory 19970801-01-PX, "IRIX ftpd Signal Handling Vulnerability" available at http://www.sgi.com/Support/Secur/security.html/ Sun Microsystems, Inc.Not vulnerable.This document is available from: http://www.cert.org/advisories/CA-1997-16.html CERT/CC Contact Information
Phone: +1 412-268-7090 (24-hour hotline) Fax: +1 412-268-6989 Postal address: CERT/CC personnel answer the hotline 08:00-17:00 EST(GMT-5) / EDT(GMT-4) Monday through Friday; they are on call for emergencies during other hours, on U.S. holidays, and on weekends. Using encryptionWe strongly urge you to encrypt sensitive information sent by email. Our public PGP key is available from If you prefer to use DES, please call the CERT hotline for more information. Getting security informationCERT publications and other security information are available from our web site
* "CERT" and "CERT Coordination Center" are registered in the U.S. Patent and Trademark Office.
NO WARRANTY Conditions for use, disclaimers, and sponsorship information
Copyright 1997 Carnegie Mellon University. Revision History
Dec. 5, 1997 Addedd vendor information for NCR Corporation to
the Updates section.
Oct. 30, 1997 UPDATES, Vendor Information Added by CERT/CC -added information
for NCR.
Sep. 30, 1997 Updated copyright statement
Aug. 15, 1997 Section 3.1 and UPDATES - Added by CERT/CC.Vendor patch information
for Digital Equipment Corporation and Silicon Graphics, Inc.
June 3, 1997 Minor editorial formatting change.
June 9, 1997 UPDATES, Vendor Information Added by CERT/CC - added information
for Sun Microsystems, Inc.
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