Vulnerabilities in INND

Original issue date: February 20, 1997
Last revised: September 26, 1997
Updated copyright statement

A complete revision history is at the end of this file.

A second vulnerability was found in INN (InterNetNews server) after the initial publication of this advisory. We are including it in this advisory as "Topic 2" so that all INN information is in one advisory. Versions 1.5.1 and earlier are vulnerable to this second problem.

Information about the first vulnerability has been widely distributed, and we have received numerous reports of exploitation. INN 1.5 and earlier are vulnerable to this problem.

Both vulnerabilities allow unauthorized users to execute arbitrary commands on the machine running INN by sending a maliciously formed news control message. Because the problem is with the content of news control messages, attacks can be launched remotely and may reach news servers located behind Internet firewalls.

The CERT/CC staff recommends that sites upgrade to INN 1.5.1 and add the patch described in Section III.A. Until you can upgrade, you should apply two patches, as described in Section III.B. You may also want to check with your vendor. Vendors who have provided input for this advisory are listed in Sec. III.C and Appendix A.

We will update this advisory as we receive additional information. Please check advisory files regularly for updates that relate to your site.


I. Description

TOPIC 2 - ucbmail

A second vulnerability involving INN has been found. It is similar to *but not the same as* the one described in Topic 1 below.

INN itself attempts to carefully remove certain shell "metacharacters" from data in control messages before passing that data to a shell. The patch for Topic 1 fixes some of the checks that were found to be inadequate. However ucbmail, a program typically configured as the mailer INN should use, lacks similar checks. INN passes some data unchecked to this mailer, which in turn passes the data to a shell for processing.

James Brister, the current maintainer of INN, has made a patch available that checks more data before it is passed to the mailer program. Although only the ucbmail program is known to have this problem, sites are encouraged to apply the patch regardless of what mail program their INN is configured to use.

TOPIC 1 - Information provided with the initial advisory

The INN daemon (innd) processes "newgroup" and "rmgroup" control messages in a shell script (parsecontrol) that uses the shell's "eval" command. However, some of the information passed to eval comes from the message without adequate checks for characters that are special to the shell.

This permits anyone who can send messages to an INN server - almost anyone with Usenet access - to execute arbitrary commands on that server. These commands run with the uid and privileges of the "innd" process on that server. Because such messages are usually passed through Internet firewalls to a site's news server, servers behind such firewalls are vulnerable to attack. Also, the program executes these commands before checking whether the sender is authorized to create or remove newsgroups, so checks at that level (such as running pgpverify) do not prevent this problem.

As of the advisory update of March 18, 1997, we have received numerous reports that the vulnerability is being exploited.

Determining if you are vulnerable

You can determine which version of INN your site is running by connecting to the NNTP port (119) of your news server. For example:
% telnet news.your.site 119
Connected to news.your.site
Escape character is '^]'.
200 news.your.site InterNetNews server INN 1.4unoff4 05-Mar-96 ready
Type "quit" to exit the connection. Note that this does not indicate whether or not the patch recommended below has been installed.

II. Impact

(Applies to both TOPICS 1 & 2)

Remote, unauthorized users can execute arbitrary commands on the system with the same privileges as the innd (INN daemon) process. Attacks may reach news servers located behind Internet firewalls.

III. Solution

Warning: If you applied any of the solutions offered in the version of this advisory released on Feb. 20, 1997, you must add an additional patch.

(The following apply to both TOPIC 1 and TOPIC 2)

We recommend upgrading to version 1.5.1 and applying the patch developed by James Brister, the current maintainer of INN (Section III. A). If you upgraded previously, you must apply this new patch to protect against the second vulnerability. Until you can upgrade, you need to apply two patches (Section III. B). You may also want to consult your vendor. Vendors who have provided input for this advisory are listed in Sec. III.C and Appendix A.

After installing any of the patches or updates, ensure that you restart your INN server.

A. Upgrade to INN 1.5.1 and apply a patch.

The current version of INN is 1.5.1. It is not vulnerable to the first vulnerability; but it is vulnerable to the second, so a patch is necessary.

When you upgrade to INN 1.5.1, please be sure to read the README file carefully.

INN 1.5.1 and information about it are available from

http://www.isc.org/inn.html

The md5 checksum for the gzip'ed tar file is

MD5 (inn-1.5.1.tar.gz) = 555d50c42ba08ece16c6cdfa392e0ca4

The patch is available from

ftp://ftp.isc.org:/isc/inn/patches/security-patch.05

Note that the advisory originally pointed to patch 04; there was a problem with this patch. You need to install patch 05.

Checksums for patches are in the directory, along with a README.

B. If you do not upgrade to 1.5.1,

apply a patch for the version you are running and then apply the newly released patch that addresses the second vulnerability discussed in this advisory. If you are running INN 1.4sec2, you should upgrade to 1.5.1 as no patches are available.

FIRST apply:

version - patch
1.5 - ftp://ftp.isc.org/isc/inn/patches/security-patch.01
1.4sec - ftp://ftp.isc.org/isc/inn/patches/security-patch.02
1.4unoff3, 1.4unoff4 - ftp://ftp.isc.org/isc/inn/patches/security-patch.03

THEN apply (1.5.1, 1.5, 1.4sec, 1.4unoff3, 1.4unoff4)

ftp://ftp.isc.org:/isc/inn/patches/security-patch.05

Note that the advisory originally pointed to patch 04; there was a problem with this patch. You need to install patch 05.

There are md5 checksums for each file in the directory, and a README file describes what is what.

C. Consult your vendor

Below is a list of vendors who have provided information about INN. Details are in Appendix A of this advisory; we will update the appendix as we receive more information. If your vendor's name is not on this list, the CERT/CC did not hear from that vendor. Please contact your vendor directly.

Berkeley Software Design, Inc. (BSDI)
Caldera
Cray Research - A Silicon Graphics Company
Debian Linux
NEC Corporation
Netscape
Red Hat Linux


Appendix A - Vendor Information

Below is a list of the vendors who have provided information for this advisory, along with an indication about whether the information relates to the first vulnerability or both. We will update this appendix as we receive additional information. If you do not see your vendor's name, the CERT/CC did not hear from that vendor. Please contact the vendor directly.

Berkeley Software Design, Inc. (BSDI)

For TOPIC 1

We ship INN as part of our distribution. BSD/OS 2.1 includes INN 1.4sec and 2.1 users should apply the patch referenced in the advisory. BSD/OS 3.0 includes INN 1.4unoff4 and the patch for that version is already included so BSD/OS 3.0 is not vulnerable as distributed.

Caldera

For TOPIC 1

An upgrade package for Caldera OpenLinux Base 1.0 will appear at Caldera's site:

ftp://ftp.caldera.com/pub/col-1.0/updates/Helsinki/004/inn-1.5.1-2.i386.rpm

MD5 sum is:

3bcd3120b93f41577d3246f3e9276098 inn-1.5.1-2.i386.rpm

Cray Research - A Silicon Graphics Company

For TOPIC 1 and TOPIC 2

Cray Research has never shipped any news server with Unicos.

Debian Linux

For TOPIC 1

The current version of INN shipped with Debian is 1.4unoff4. However the "unstable" (or development) tree contains inn-1.5.1. It can be gotten from any debian mirror in the subdirectory

debian/unstable/binary/news

d3603d9617fbf894a3743a330544b62e 591154 news optional inn_1.5.1-1_i386.deb 205850779d2820f03f2438d063e1dc51 45230 news optional inn-dev_1.5.1-1_i386.deb badbe8431479427a4a4de8ebd6e1e150 31682 news optional inewsinn_1.5.1-1_i386.deb

NEC Corporation

For TOPIC 1 and TOPIC 2

Products below are shipped with INN mentioned in this advisory, so they are vulnerable and patches are in progress.

Goah/NetworkSV R1.2 vulnerable
Goah/NetworkSV R2.2 vulnerable
Goah/NetworkSV R3.1 vulnerable
Goah/IntraSV R1.1 vulnerable

Netscape

For Topic 2

The Netscape News Server 2.01 and current beta (and future shipping) versions of Netscape Collabra Server are NOT vulnerable to this problem because the Netscape News Server uses its own mailer instead of 'ucbmail'. The Netscape News Server mailer is a simple SMTP front-end that DOES NOT pass anything to the shell. Hence it is immune to the vulnerability outlined in topic 2 of the advisory.

Netscape News Server 1.1 users should apply the patch recommended by the Cert Advisory to solve this problem.

For Topic 1
The Netscape News Server 2.01 is immune to the attack outlined in the advisory.

The News Server 1.1 is, however, subject to the same vulnerability as INN and we have advised customers to install the patch described in the advisory.

Red Hat Linux

For Topics 1 and 2

There is a critical security hole in INN which affects all versions of Red Hat Linux. A new version, inn-1.5.1-6, is now available for Red Hat Linux 4.0 and 4.1 for all platforms. If you are running an earlier version of Red Hat, we strongly encourage you to upgrade to 4.1 as soon as possible, as many critical security fixes have been made. The new version of inn is PGP signed with the Red Hat PGP key, which is available on all Red Hat CDROMs, ftp.redhat.com, and public keyservers.

You may upgrade to the new version as follows:

Red Hat 4.1

i386:

rpm -Uvh ftp://ftp.redhat.com/updates/4.1/i386/inn-1.5.1-6.i386.rpm

alpha:

rpm -Uvh ftp://ftp.redhat.com/updates/4.1/alpha/inn-1.5.1-6.alpha.rpm

rpm -Uvh ftp://ftp.redhat.com/updates/4.1/sparc/inn-1.5.1-6.sparc.rpm

Red Hat 4.0

i386:

rpm -Uvh ftp://ftp.redhat.com/updates/4.0/i386/inn-1.5.1-6.i386.rpm

alpha:

rpm -Uvh ftp://ftp.redhat.com/updates/4.0/alpha/inn-1.5.1-6.alpha.rpm

SPARC

rpm -Uvh ftp://ftp.redhat.com/updates/4.0/sparc/inn-1..5.1-6.sparc.rpm

The CERT Coordination Center thanks James Brister of the Internet Software Consortium for making fixes available and Matt Power of MIT for analyzing and reporting the first problem. We also thank AUSCERT for their contributions to this advisory. James Crawford Ralston of the University of Pittsburgh and Frank Miller of Tektronix Corporation assisted with the March 18, 1997 update.

The second vulnerability addressed in this advisory was discovered by security experts in the Global Security Analysis Laboratory (GSAL) at IBM's T.J. Watson Research Center. We thank the IBM Emergency Response Service for providing information on this topic. (They published information in ERS-SVA-E01-1997:002.1. Their alert is copyrighted 1997 by International Business Machines Corporation.)

UPDATES

August 15, 1997

The current version is inn-1.5.1sec2, and is available from:
ftp://ftp.isc.org/isc/inn/inn-1.5.1sec2.tar.gz

March 18, 1997

If you are upgrading to INN 1.5.1, please be sure to read the README file carefully. Note that if you are upgrading to 1.5.1 from a previous release, running a "make update" alone is not sufficient to ensure that all of the vulnerable scripts are replaced (e.g., parsecontrol). Please especially note the following from the INN 1.5.1 distribution README file:

When updating from a previous release, you will usually want to do "make update" from the top-level directory; this will only install the programs. To update your scripts and config files, cd into the "site" directory and do "make clean" -- this will remove any files that are unchanged from the official release. Then do "make diff >diff"; this will show you what changes you will have to merge in. Now merge in your changes (from where the files are, ie. /usr/lib/news...) into the files in $INN/site. (You may find that due to the bug fixes and new features in this release, you may not need to change any of the scripts, just the configuration files). Finally, doing "make install" will install everything.

After installing any of the patches or updates, ensure that you restart your INN server.


Copyright 1997 Carnegie Mellon University.


Revision History
Sep. 26, 1997 Updated copyright statement
Aug. 15, 1997 UPDATES - added information about the latest release.
Apr 04, 1997  Appendix A - added information from Netscape about Topic
              2 Solution sections III.A and B - replaced pointer to
              patch 04 with patch 05 and noted that you must use patch
              05 Contact information corrected the URL for FIRST
Apr 03, 1997  Added information on a second vulnerability (labeled
              Topic 2), including a new patch that must be applied to
              many versions of INN.  Labeled vendor information as
              input on Topic 1 or 2.
Mar 25, 1997  Section III.B - added a note that no patches are
              available for version 1.4sec2.
Mar 24, 1997  Appendix A - added information from Netscape.
Mar 21, 1997  Appendix A - added information from NEC Corporation.
Mar 18, 1997  Updates section - added a caution for sites upgrading to
              1.5.1 Acknowledgments - added J. C. Ralston and F. Miller
Mar 17, 1997  Section III.B - corrected patch information (patch.03
              must be used for 1.4unoff3, 1.4unoff4 rather than
              patch.01); added a URL for INN information.
              Section III.A and introduction - noted that the
              vulnerability is being actively exploited.