8131554 2002-03-12 13:45 -0500 /386 rader/ CERT Advisory <cert-advisory@cert.org>
Sänt av: owner-root@lysator.liu.se
Importerad: 2002-03-12 23:43 av Brevbäraren
Extern mottagare: cert-advisory@cert.org
Mottagare: Bellman -- The Recursive Hacker <17140>
Mottaget: 2002-03-12 23:55
Mottagare: Bugtraq (import) <21400>
Sänt: 2002-03-13 19:54
Ärende: CERT Advisory CA-2002-07 Double Free Bug in zlib Compression Library
------------------------------------------------------------
From: CERT Advisory <cert-advisory@cert.org>
To: cert-advisory@cert.org
Message-ID: <CA-2002-07.1@cert.org>
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CERT Advisory CA-2002-07 Double Free Bug in zlib Compression Library
Original release date: March 12, 2002
Last revised: --
Source: CERT/CC
A complete revision history can be found at the end of this file.
Systems Affected
* Any software that is linked to zlib 1.1.3 or earlier may be
affected
* Data compression libraries derived from zlib 1.1.3 or earlier may
contain a similar bug
Overview
There is a bug in the zlib compression library that may
manifest itself as a vulnerability in programs that are linked
with zlib. This may allow an attacker to conduct a
denial-of-service attack, gather information, or execute arbitrary
code.
It is important to note that the CERT/CC has not received any
reports of exploitation of this bug. Based on the information
available to us at this time, it is difficult to determine
whether this bug can be successfully exploited. However, given
the widespread deployment of zlib, we have published this document
as a proactive measure.
I. Description
There is a bug in the decompression algorithm used by the popular zlib
compression library. If an attacker is able to pass a
specially-crafted block of invalid compressed data to a program that
includes zlib, the program's attempt to decompress the crafted data
can cause the zlib routines to corrupt the internal data structures
maintained by malloc.
The bug results from a programming error that causes segments of
dynamically allocated memory to be released more than once (i.e.,
"double-freed"). Specifically, when inftrees.c:huft_build() encounters
the crafted data, it returns an unexpected Z_MEM_ERROR to
inftrees.c:inflate_trees_dynamic(). When a subsequent call is made to
infblock.c:inflate_blocks(), the inflate_blocks function tries to free
an internal data structure a second time.
Because this bug interferes with the proper allocation and
deallocation of dynamic memory, it may be possible for an attacker to
influence the operation of programs that include zlib. In most
circumstances, this influence will be limited to denial of service or
information leakage, but it is theoretically possible for an attacker
to insert arbitrary code into a running program. This code would be
executed with the permissions of the vulnerable program.
The CERT/CC is tracking this issue as VU#368819. This reference
number corresponds to CVE candidate CAN-2002-0059.
II. Impact
This bug may introduce vulnerabilities into any program that
includes the affected library. Depending upon how and where the
zlib routines are called from the given program, the resulting
vulnerability may have one or more of the following
impacts: denial of service, information leakage, or execution of
arbitrary code.
III. Solution
Upgrade your version of zlib
The maintainers of zlib have released version 1.1.4 to address
this vulnerability. Upgrade any software that is linked to or
derived from an earlier version of zlib. The latest version of
zlib is available at http://www.zlib.org
These are the MD5 checksums for zlib version 1.1.4:
abc405d0bdd3ee22782d7aa20e440f08 zlib-1.1.4.tar.gz
9bf1d36ced334b0cf1f996f5c8171018 zlib114.zip
Apply a patch from your vendor
The zlib compression library is freely available and used by many
vendors in a wide variety of applications. Any one of these
applications may contain vulnerabilities that are introduced by this
vulnerability.
Appendix A contains information provided by vendors for this
advisory. As vendors report new information to the CERT/CC, we
will update this section and note the changes in our revision
history. If a particular vendor is not listed below, we have
not received their comments. Please contact your vendor directly.
Appendix A. - Vendor Information
This appendix contains information provided by vendors for
this advisory. As vendors report new information to the
CERT/CC, we will update this section and note the changes in our
revision history. If a particular vendor is not listed below,
we have not received their comments.
Apple Computer, Inc.
Mac OS X and Mac OS X Server do not contain this vulnerability.
Compaq Computer Corporation
COMPAQ COMPUTER CORPORATION
-----------------------------
x-ref: SSRT0818 zlib
At the time of writing this document, Compaq continues to
evaluate this potential problem and impacts to Compaq released
software. Compaq will implement solutions based on the conclusion
of this evaluation as necessary. Compaq will provide notice of
any new patches as a result any required solution through
standard patch notification procedures and be available from your
normal Compaq Services support channel. COMPAQ COMPUTER
CORPORATION
-----------------------------
Conectiva Linux
Conectiva Linux supported versions (5.0, 5.1, 6.0, 7.0,
ferramentas graficas and ecomerce) are affected by the zlib
vulnerability. Updates will be sent to our security mailing lists
and be available at our ftp site and mirrors. The updates
will include a new version of zlib itself and also other packages
which include their own version of zlib or are linked statically
to the system-wide copy of zlib.
Engarde
EnGarde Secure Linux Community and Professional are both
vulnerable to the zlib bugs. Guardian Digital addressed this
vulnerability in ESA-20020311-008 which may be found at:
http://www.linuxsecurity.com/advisories/other_advisory-1960.html
EnGarde Secure Professional users may upgrade their systems using
the Guardian Digital Secure Network.
FreeBSD
FreeBSD is not vulnerable, as the FreeBSD malloc
implementation detects and complains about several programming
errors including this kind of double free.
Fujitsu
Fujitsu's UXP/V operating system is not affected by the zlib
vulnerability because it does not support zlib.
Hewlett-Packard Company
HP is not vulnerable.
IBM Corporation
IBM's AIX operating system, version 5.1, ships with open
source-originated zlib that is used with the Redhat Package Manager
(rpm) to install applications that are included in the AIX-Linux
Affinity Toolkit. zlib (libz.a) is a shared library in AIX. AIX 5.1 is
susceptible to the described vulnerability. AIX 4.3.x does not ship
with zlib, but customers who install zlib and use it will be similarly
vulnerable. IBM will make the patched version of zlib available as
soon as it is made available to us.
OpenBSD
OpenBSD is not vulnerable as OpenBSD's malloc implementation
detects double freeing of memory. The zlib shipped with OpenBSD
has been fixed in OpenBSD-current in January 2002.
Openwall GNU/*/Linux
All versions of Openwall GNU/*/Linux (Owl) prior to the 2002/02/15
Owl-current snapshot are affected by the zlib double-free
vulnerability. Owl-current after 2002/02/15 includes the proper fixes
in its userland packages. In order to not place the users of other
vendors' products at additional risk, we have agreed to delay
documenting this as a security change and including the fixes in Owl
0.1-stable until there's a coordinated public announcement. While we
don't normally support this kind of a policy (releasing a fix before
there's an announcement), this time handling the vulnerability in this
way was consistent with the state of things by the time the (already
publicly known) bug was first realized to be a security vulnerability.
The zlib bug could affect the following Owl packages: gnupg,
openssh, rpm, texinfo (not necessarily in a security
sense). Of these, the OpenSSH could potentially allow for an
active remote attack resulting in a root compromise. If only SSH
protocol version 1 is allowed in the OpenSSH server this is
reduced to a local attack, but reverse remote attack
possibilities by a malicious server remain. Additionally, any
third-party software that makes use of the provided zlib library
could be affected.
Parts of the Linux 2.2 kernel included in Owl were also
affected by the vulnerability. Fortunately, those parts
(Deflate compression support for PPP and the experimental
Deflate compression extension to IrDA) are normally not used
by the Owl userland. The bug has been corrected starting with
Linux 2.2.20-ow2 which has been made public and a part of both
Owl-current and Owl 0.1-stable on 2002/03/03. This change,
however, will only be documented in the publicly-available
change logs on the coordinated public announcement date.
Red Hat, Inc.
Red Hat Linux ships with a zlib library that is vulnerable to
this issue. Although most packages in Red Hat Linux use the
shared zlib library we have identified a number of packages that
either statically link to zlib or contain an internal version of
the zlib code.
Updates to zlib and these packages as well as our advisory note
are available from the following URL. Users of the Red Hat Network
can use the up2date tool to automatically upgrade their systems.
http://www.redhat.com/support/errata/RHSA-2002-026.html
Red Hat would like to thank CERT/CC for their help in
coordinating this issue with other vendors.
SGI
SGI acknowledges the zlib vulnerabilities reported by CERT
and is currently investigating. No further information is
available at this time.
For the protection of all our customers, SGI does not disclose,
discuss or confirm vulnerabilities until a full investigation has
occurred and any necessary patch(es) or release streams are available
for all vulnerable and supported IRIX operating systems. Until SGI has
more definitive information to provide, customers are encouraged to
assume all security vulnerabilities as exploitable and take
appropriate steps according to local site security policies and
requirements. As further information becomes available, additional
advisories will be issued via the normal SGI security information
distribution methods including the wiretap mailing list on
http://www.sgi.com/support/security/.
XFree86
XFree86 versions 4.0 through 4.2.0 include zlib version 1.0.8. XFree86
3.x includes zlib version 1.0.4. The zlib code included with XFree86
is only used on some platforms. This is determined by the setting of
HasZlib in the imake config files in the xc/config/cf source
directory. If HasZlib is set to YES in the platform's vendor.cf
file(s), then the system-provided zlib is used instead of the
XFree86-provided version. XFree86 uses the system-provided zlib by
default only on the following platforms:
FreeBSD 2.2 and later
NetBSD 1.2.2 and later
OpenBSD
Darwin
Debian Linux
The zlib code in XFree86 has been fixed in the CVS repository
(trunk and the xf-4_2-branch branch) as of 14 February 2002. A
source patch for XFree86 4.2.0 will be available from
ftp://ftp.xfree86.org/pub/XFree86/4.2.0/fixes/.
The following XFree86 4.2.0 binary distributions provided by
XFree86 include and use a vulnerable version of zlib:
Linux-alpha-glibc22
Linux-ix86-glibc22
When updated binaries are available, it'll be documented at
http://www.xfree86.org/4.2.0/UPDATES.html.
To check if an installation of XFree86 includes zlib, see if
the following file exists:
/usr/X11R6/lib/libz.a
To check if an XFree86 X server is dynamically linked with zlib, look
for a line containing 'libz' in the output of 'ldd
/usr/X11R6/bin/XFree86'.
Various vendors repackage and distribute XFree86, and may use
settings and configurations different from those described here.
zlib.org
All users of zlib versions 1.1.3 or earlier should obtain the
latest version, 1.1.4 or later, from http://www.zlib.org, in
order to avoid this vulnerability as well as other possible
vulnerabilities in versions prior to 1.1.3 when decompressing
invalid data.
Appendix B. - References
* http://bugzilla.gnome.org/show_bug.cgi?id=70594
* http://www.kb.cert.org/vuls/id/368819
* http://www.libpng.org/pub/png/pngapps.html
* http://www.redhat.com/support/errata/RHSA-2002-026.html
_________________________________________________________________
The CERT/CC thanks Owen Taylor and Mark Cox of Red Hat, Inc. for
reporting this vulnerability. We also thank Mark Adler of zlib.org for
contributing to our research and Matthias Clasen for contributing to
the discovery of this vulnerability.
_________________________________________________________________
This document was written by Jeffrey P. Lanza.
______________________________________________________________________
This document is available from:
http://www.cert.org/advisories/CA-2002-07.html
______________________________________________________________________
CERT/CC Contact Information
Email: cert@cert.org
Phone: +1 412-268-7090 (24-hour hotline)
Fax: +1 412-268-6989
Postal address:
CERT Coordination Center
Software Engineering Institute
Carnegie Mellon University
Pittsburgh PA 15213-3890
U.S.A.
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 encryption
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http://www.cert.org/CERT_PGP.key
If you prefer to use DES, please call the CERT hotline for
more information.
Getting security information
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______________________________________________________________________
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Conditions for use, disclaimers, and sponsorship information
Copyright 2002 Carnegie Mellon University.
Revision History
Mar 12, 2002: Initial release
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