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SuSE Linux 8.0: 2002:032 Critical: Local Privilege Escalation in LibX11

The libX11 library from this package dynamically loads other libraries where the pathname is controlled by the user invoking the program linked against libX11. Unfortunately, libX11 also behaves the same way when linked against setuid programs. This behavior allows local users to execute arbitrary code under a different UID which can be the root-UID in the worst case.. ______________________________________________________________________________ SuSE Security Announcement Package: xf86 Announcement-ID: SuSE-SA:2002:032 Date: Wed Sep 18 12:00:00 MEST 2002 Affecte products: SuSE Linux 8.0 Vulnerability Type: local privilege escalation Severity (1-10): 5 SuSE default package: yes Cross References: Content of this advisory: 1) security vulnerability resolved: LD_PRELOAD vulnerability in the X11 library problem description, discussion, solution and upgrade information 2) pending vulnerabilities, solutions, workarounds: - Perl 5.6.1 glob overflow fix - new OpenSSH packages - sparc info 3) standard appendix (further information) ______________________________________________________________________________ 1) problem description, brief discussion, solution, upgrade information The xf86 package contains various libraries and programs which are fundamental for the X server to function. The libX11.so library from this package dynamically loads other libraries where the pathname is controlled by the user invoking the program linked against libX11.so. Unfortunately, libX11.so also behaves the same way when linked against setuid programs. This behavior allows local users to execute arbitrary code under a different UID which can be the root-UID in the worst case. libX11.so has been fixed to check for calls from setuid programs. It denies loading of user controlled libraries in this case. We recommend an update in any case since there is no easy workaround possible except removing the setuid bit from any program linked against libX11.so. 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-8.0 2a515055a811de5b465d016ffa77a09c 67ddeb24b04b8c2badb7a039d9ea270e source rpm: e44b3f6dd4a406bd422adc4f7fac63f2 ______________________________________________________________________________ 2) Pending vulnerabilities in SuSE Distributions and Workarounds: - perl New Perl 5.6.1 packages will soon be available which fix overflows in the globbing code of the Perl interpreter. Although we believe that there is not much impact by this bug, we recommend an update especially on systems offering remote services based on Perl. - openssh New openssh packages are available for the SuSE Linux distributions 7.0 - 7.3 (version 2.9.9p2). These packages have been rebuilt to contain the fixes in the openssl library, which is used by openssh. It is possible but not proven that the weaknesses in the openssl code (fixed and announced by SuSE-SA:2002:027) can be exploited in any way. We release the packages to prevent the possibility that the vulnerability exists. It is recommended to install the updates. - sparc Due to a lack of build power on the sparc architecture, we will discontinue providing security updates for the SuSE Linux 7.0 and 7.1 distributions for sparc. We estimate that more than 95% of all SuSE Linux for sparc users use the most recent version 7.3 so that the loss should be considerably small. In addition to the update directories on ftp.suse.com, we will also move the directories containing the distributions themselves into the discontinued/ tree on ftp.suse.com/pub/suse/discontinued/. By consequence, all updates will continue to be available, but the path indicates that these directories and files will remain there for archiving purposes only. Please note that mirrors of the SuSE ftp server ftp.suse.com might not contain the discontinued/ directory tree. ______________________________________________________________________________ 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 authenticityof 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 un-installed 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 top-level 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 announcements are sent to this list. To subscribe, send an email to . For generalinformation 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 clear-text signature shows proof of the authenticity of the text. SuSE Linux AG makes no warranties of any kind whatsoever with respect to the information contained in this security advisory. Type Bits/KeyID Date User ID pub 2048R/3D25D3D9 1999-03-06 SuSE Security Team pub 1024D/9C800ACA 2000-10-19 SuSE Package Signing Key . Debian Security Alert concerning libX11 reveals critical local privilege escalation flaws, prompting swift patch deployment for urgent resolution.. Local Privilege Escalation, SuSE Linux 8.0 Issues, LibX11 Security Fix. . Severity: Critical. LinuxSecurity.com Team

Sep 19, 2002 •Critical SuSE