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security advisorymoderate severityremote command execution

SuSE: 2002:010 Moderate: Remote Command Execution Risk In Libz/Zlib

An error in a decompression routine can corrupt the internal data structures of malloc by a double call to the free() function. If the data processed by the compression library is provided from an untrusted source, it may be possible for an attacker to interfere with the process using the zlib routines.. ______________________________________________________________________________ SuSE Security Announcement Package: libz/zlib Announcement-ID: SuSE-SA:2002:010 Date: Monday, Mar 11th 2002 20:45 MET Affected products: 6.4, 7.0, 7.1, 7.2, 7.3 SuSE Linux Database Server SuSE eMail Server III SuSE Firewall SuSE Linux Connectivity Server SuSE Linux Enterprise Server 7 Vulnerability Type: remote command execution Severity (1-10): 8 SuSE default package: yes Other affected systems: systems with recent versions of the compression library Content of this advisory: 1) security vulnerability resolved: libz/zlib problem description, discussion, solution and upgrade information 2) pending vulnerabilities, solutions, workarounds 3) standard appendix (further information) ______________________________________________________________________________ 1) problem description, brief discussion, solution, upgrade information The zlib compression library is being used by many applications to provide data compression/decompression routines. An error in a decompression routine can corrupt the internal data structures of malloc by a double call to the free() function. If the data processed by the compression library is provided from an untrusted source, it may be possible for an attacker to interfere with the processusing the zlib routines. The attack scenario includes a denial of service attack and memory/data disclosure, but it may also be possible to insert arbitrary code into the running program and to execute this code. This update fixes the known problems in the libz/zlib as a permanent fix. There exists no temporary workaround that can efficiently remedy the problem. It is expected that a large range of software is affected. The systems affected are by no means limited to Linux systems or other open-source based operating systems. Note: The libz compression library is being used by several hundred packages in all SuSE products. While the update of the libz package as itself is not problematic, it must be noted that many packages bring their own compression library in their source code. If these packages link against their own version of the libz compression library, their source needs to be fixed as well. Considering the length of a combined Security Announcement, SuSE Security publish a tandem-announcement, consisting of two seperate Security Announcements released in quick succession: SuSE-SA:2002:010 libz/zlib SuSE-SA:2002:011 packages containing libz/zlib Acknowledgements: We thank Owen Taylor who tracked down the bug in the compression library, and to Matthias Clasen for reporting the problem that seemed to be located in the libpng at first. We also thank Mark Adler and Jean-loup Gailly, the authors of the zlib package, for their quick response in the double-free() matter. SPECIAL INSTALL INSTRUCTIONS: ============================== * Installation of the update package: The installation of shared libraries on an actively running system should be done with special care. During the update of the libz package, runtime-linking the shared libraries is likely to fail for processes that execute a new binary with the execve(2) system call. If at all applicable, asystem receiving the update should be kept as quiet as possible during the time that the RPM command runs. In doubt, please perform the update in Single User Mode ("init S"). The RPM command must not be interrupted during its operation. After performing the update, the processes that still use the old version of the package must be restarted for the libz upgrade to become effective. If you have performed the update in Single User Mode, this has been done already, and you can safely return to your default runlevel. If in doubt, reboot your system to make sure that the changes are becoming effective. Please download the update package for your distribution and verify its integrity by the methods listed in section 3) of this announcement. Then, install the package using the command "rpm -Fhv file.rpm" to apply the update. Our maintenance customers are being notified individually. The packages are being offered to install from the maintenance web. i386 Intel Platform: SuSE-7.3 799491ca29f9bf95e3e38a73f25abea8 source rpm: a4071506da6ab39dca5495530028d291 SuSE-7.2 2197aff65b09fb05b8969ace64d7a4a6 source rpm: 1694ed149ca946e7ea1cc2da3f14c181 SuSE-7.1 c309b104231c596bb81008c38a4e473c source rpm: 950c86970cd7c3fc0a30cfab176769ac SuSE-7.0 8bde6b53a78e5f920080bfa3b6a236a6 source rpm: 718c36c91cd0f97466cbb2303967d51c SuSE-6.4 270fc89c1be6854288925a9326f9ca6e source rpm: 625ed87653f820f7f65a4a8e045f6cc2 Sparc Platform: SuSE-7.3 f890b6d04e9164fc2afa05241c0e94c9 source rpm: 818d39946dc6c73f425620fba546935c SuSE-7.1 ff4ea0da2c5126311f654b2896a70dd9 source rpm: c3a49ea61f2642d53e29c8a81e07bfd9 SuSE-7.0 b9e22f0ff9785ca1d226bd2c5e135909 source rpm: 25c2b7cd4e20da69b7d806551966bae8 AXP Alpha Platform: SuSE-7.1 e8cd8561a1434c36afcccd856d79a483 source rpm: f7c21774f76fb240205291c4e91ad83c SuSE-7.0 15510fc7563e669145d28a69e0e77d8e source rpm: 008bc8f743e64e26dccd89baf882b214 SuSE-6.4 7d29b7d929e4b36dd6268058bf3c7538 source rpm: 67a4bd496c7625aaa3049417930e97f8 PPC Power PC Platform: SuSE-7.3 b06097a1496ca5fd7b3492c2ab4f7337 source rpm: 45127ca06e4b019b2e700a0c87c2edb6 SuSE-7.1 783a39b17295e169d344a5f7f1ad7e86 source rpm: 2ac1e404e8a6723b1eb101b7c7d118e8 SuSE-7.0 24901e0c7ccb6bf5bf17b2af60596d96 source rpm: f9e6cda577a5007baa84fb9940ec718d SuSE-6.4 b3580d5e1b3702c330957bde4422486c source rpm: 32cbca2dbc911da128b5bd1d19789792 ______________________________________________________________________________ 2) Pending vulnerabilities in SuSE Distributions and Workarounds: - Please see the following SuSE Security Announcement SuSE-SA:2002:011 (packages containing libz) for upgrade information regarding packages that bring their own compression library in their source. ______________________________________________________________________________ 3) standard appendix: authenticity verification, additional information - Package authenticity verification: SuSE update packages are available on many mirror ftp servers all over the world. While this service is being considered valuable and important to the free and open source software community, many users wish to be sure about the origin of the package and its content before installing the package. There are two verification methods that can be used independently from each other to prove the authenticity of a downloaded file or rpm package: 1) md5sums as provided in the (cryptographically signed)announcement. 2) using the internal gpg signatures of the rpm package. 1) execute the command md5sum after you downloaded the file from a SuSE ftp server or its mirrors. Then, compare the resulting md5sum with the one that is listed in the announcement. Since the announcement containing the checksums is cryptographically signed (usually using the key This email address is being protected from spambots. You need JavaScript enabled to view it. ), the checksums show proof of the authenticity of the package. We disrecommend to subscribe to security lists which cause the email message containing the announcement to be modified so that the signature does not match after transport through the mailing list software. Downsides: You must be able to verify the authenticity of the announcement in the first place. If RPM packages are being rebuilt and a new version of a package is published on the ftp server, all md5 sums for the files are useless. 2) rpm package signatures provide an easy way to verify the authenticity of an rpm package. Use the command rpm -v --checksig to verify the signature of the package, where is the filename of the rpm package that you have downloaded. Of course, package authenticity verification can only target an uninstalled rpm package file. Prerequisites: a) gpg is installed b) The package is signed using a certain key. The public part of this key must be installed by the gpg program in the directory ~/.gnupg/ under the user's home directory who performs the signature verification (usually root). You can import the key that is used by SuSE in rpm packages for SuSE Linux by saving this announcement to a file ("announcement.txt") and running the command (do "su -" to be root): gpg --batch; gpg < announcement.txt | gpg --import SuSE Linux distributions version 7.1 and thereafter install the key " This email address is being protected from spambots. You need JavaScript enabled to view it. " upon installation or upgrade, provided that the package gpg is installed. The file containing the public key is placed at the toplevel directory of the first CD (pubring.gpg) and at . - SuSE runs two security mailing lists to which any interested party may subscribe: This email address is being protected from spambots. You need JavaScript enabled to view it. - general/linux/SuSE security discussion. All SuSE security announcements are sent to this list. To subscribe, send an email to . This email address is being protected from spambots. You need JavaScript enabled to view it. - SuSE's announce-only mailing list. Only SuSE's security annoucements are sent to this list. To subscribe, send an email to . For general information or the frequently asked questions (faq) send mail to: or respectively. ==================================================================== SuSE's security contact is or . The public key is listed below. ====================================================================______________________________________________________________________________ The information in this advisory may be distributed or reproduced, provided that the advisory is not modified in any way. In particular, it is desired that the cleartext signature shows proof of the authenticity of the text. SuSE GmbH makes no warranties of any kind whatsoever with respect to the information contained in this security advisory. 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Libz/Zlib faced a moderate risk due to a remote command execution issue. Immediate updates are advised.. Libz Vulnerability, Zlib Exploit, Data Integrity, Execution Risk, SuSE Security. . Severity: Important. LinuxSecurity.com Team

Mar 11, 2002 •Important SuSE