__________________________________________________________ The U.S. Department of Energy Computer Incident Advisory Capability ___ __ __ _ ___ / | /_\ / \___ __|__ / \ \___ __________________________________________________________ INFORMATION BULLETIN Red Hat Linux Password Locking Race Vulnerability [RHSA-2002:132-19] July 30, 2002 19:00 GMT Number M-104 [Revised 14 July 03] ______________________________________________________________________________ PROBLEM: A locally exploitable vulnerability is present in the util-linux package shipped with Red Hat Linux. PLATFORM: Red Hat Linux 7.3 and earlier DAMAGE: Under certain conditions, a carefully crafted attack sequence can be performed to exploit a complex file locking and modification race present in this utility allowing changes to be made to /etc/passwd. SOLUTION: All users of Red Hat Linux should update to the errata util-linux packages which contain a patch to correct this vulnerability. ______________________________________________________________________________ VULNERABILITY The risk is LOW. A carefully crafted attack sequence can be ASSESSMENT: performed to exploit this vulnerability. In order to successfully exploit the vulnerability and perform privilege escalation there is a need for minimal administrator interaction. ______________________________________________________________________________ LINKS: CIAC BULLETIN: http://www.ciac.org/ciac/bulletins/m-104.shtml ORIGINAL BULLETIN: http://rhn.redhat.com/errata/RHSA-2002-132.html ______________________________________________________________________________ Revision History: 07/10/03 - Added packages for Red Hat Linux on IBM iSeries and pSeries systems. [***** Start RHSA-2002:132-19 *****] Updated util-linux package fixes password locking race Advisory: RHSA-2002:132-19 Last updated on: 2003-07-10 Affected Products: Red Hat Linux 6.2 Red Hat Linux 7.0 Red Hat Linux 7.1 Red Hat Linux 7.1 for iSeries Red Hat Linux 7.1 for pSeries Red Hat Linux 7.2 Red Hat Linux 7.3 CVEs (cve.mitre.org): CVE-2002-0638 Security Advisory Details: A locally exploitable vulnerability is present in the util-linux package which shipped with Red Hat Linux. [Updated 8 July 2003] Added packages for Red Hat Linux on IBM iSeries and pSeries systems. The util-linux package contains a large variety of low-level system utilities that are necessary for a Linux system to function. The chfn utility included in this package allows users to modify personal information stored in the system-wide password file, /etc/passwd. In order to modify this file, this application is installed setuid root. Under certain conditions, a carefully crafted attack sequence can be performed to exploit a complex file locking and modification race present in this utility allowing changes to be made to /etc/passwd. In order to successfully exploit the vulnerability and perform privilege escalation there is a need for minimal administrator interaction. Additionally, the password file must be over 4 kilobytes, and the local attackers entry must not be in the last 4 kilobytes of the password file. The Common Vulnerabilities and Exposures project (cve.mitre.org) has assigned the name CAN-2002-0638 to this issue. An interim workaround is to remove setuid flags from /usr/bin/chfn and /usr/bin/chsh. All users of Red Hat Linux should update the packages contained in this erratum, which are patched to correct this vulnerability. Many thanks to Michal Zalewski of Bindview for alerting us to this issue. Updated packages: Red Hat Linux 6.2 -------------------------------------------------------------------------------- SRPMS: util-linux-2.10f-7.6.2.src.rpm [ via FTP ] [ via HTTP ] 0af6265f350849394fc54ca7f006fd82 alpha: util-linux-2.10f-7.6.2.alpha.rpm [ via FTP ] [ via HTTP ] 4e30115e7fd311ac8496637c03716473 i386: util-linux-2.10f-7.6.2.i386.rpm [ via FTP ] [ via HTTP ] e1c0e740d41aaddc7817604ed449e872 sparc: util-linux-2.10f-7.6.2.sparc.rpm [ via FTP ] [ via HTTP ] fe28b4c80b9fe909c38f913b899ddb16 Red Hat Linux 7.0 -------------------------------------------------------------------------------- SRPMS: util-linux-2.10m-12.7.0.src.rpm [ via FTP ] [ via HTTP ] 4aa3502469cc8255aea825cebe82d4db alpha: util-linux-2.10m-12.7.0.alpha.rpm [ via FTP ] [ via HTTP ] b2e1b30a837e440297acba35d13fab77 i386: util-linux-2.10m-12.7.0.i386.rpm [ via FTP ] [ via HTTP ] af9aca214e81e4f306d49ed398a79f22 Red Hat Linux 7.1 -------------------------------------------------------------------------------- SRPMS: util-linux-2.11f-17.7.2.src.rpm [ via FTP ] [ via HTTP ] dc87f0566da2f6a37443f9614cb1ff61 alpha: util-linux-2.11f-17.7.2.alpha.rpm [ via FTP ] [ via HTTP ] c3bc4100fdc6e4e7c4b524c16991f168 i386: util-linux-2.11f-17.7.2.i386.rpm [ via FTP ] [ via HTTP ] 668e4b28b07dcd9718744b2c59383bc2 ia64: util-linux-2.11f-17.7.2.ia64.rpm [ via FTP ] [ via HTTP ] 200e1661f445fca662f51d810f650448 Red Hat Linux 7.1 for iSeries -------------------------------------------------------------------------------- SRPMS: util-linux-2.11f-17.7.2.src.rpm [ via FTP ] [ via HTTP ] dc87f0566da2f6a37443f9614cb1ff61 ppc: util-linux-2.11f-17.7.2.ppc.rpm [ via FTP ] [ via HTTP ] 39b2f33573da14946639e38f7dbccaec Red Hat Linux 7.1 for pSeries -------------------------------------------------------------------------------- SRPMS: util-linux-2.11f-17.7.2.src.rpm [ via FTP ] [ via HTTP ] dc87f0566da2f6a37443f9614cb1ff61 ppc: util-linux-2.11f-17.7.2.ppc.rpm [ via FTP ] [ via HTTP ] 39b2f33573da14946639e38f7dbccaec Red Hat Linux 7.2 -------------------------------------------------------------------------------- SRPMS: util-linux-2.11f-17.7.2.src.rpm [ via FTP ] [ via HTTP ] dc87f0566da2f6a37443f9614cb1ff61 i386: util-linux-2.11f-17.7.2.i386.rpm [ via FTP ] [ via HTTP ] 668e4b28b07dcd9718744b2c59383bc2 ia64: util-linux-2.11f-17.7.2.ia64.rpm [ via FTP ] [ via HTTP ] 200e1661f445fca662f51d810f650448 Red Hat Linux 7.3 -------------------------------------------------------------------------------- SRPMS: util-linux-2.11n-12.7.3.src.rpm [ via FTP ] [ via HTTP ] 474988909a18c0f73a65de40bf946e92 i386: losetup-2.11n-12.7.3.i386.rpm [ via FTP ] [ via HTTP ] b1b6d7852f75d1014204b7853f656427 mount-2.11n-12.7.3.i386.rpm [ via FTP ] [ via HTTP ] 496ec0a9c0720ba5bed7baa917114aac util-linux-2.11n-12.7.3.i386.rpm [ via FTP ] [ via HTTP ] da8c81ee48c180694b89c9c99f543256 Solution Before applying this update, make sure all previously released errata relevant to your system have been applied. To update all RPMs for your particular architecture, run: rpm -Fvh [filenames] where [filenames] is a list of the RPMs you wish to upgrade. Only those RPMs which are currently installed will be updated. Those RPMs which are not installed but included in the list will not be updated. Note that you can also use wildcards (*.rpm) if your current directory *only* contains the desired RPMs. Please note that this update is also available via Red Hat Network. Many people find this an easier way to apply updates. To use Red Hat Network, launch the Red Hat Update Agent with the following command: up2date This will start an interactive process that will result in the appropriate RPMs being upgraded on your system. References: http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2002-0638 http://www.kb.cert.org/vuls/id/405955 http://razor.bindview.com/publish/advisories/adv_chfn.html Keywords: locking, password, race, util-linux -------------------------------------------------------------------------------- The listed packages are GPG signed by Red Hat, Inc. for security. Our key is available at: http://www.redhat.com/solutions/security/news/publickey/#key You can verify each package and see who signed it with the following command: rpm --checksig -v filename If you only wish to verify that each package has not been corrupted or tampered with, examine only the md5sum with the following command: md5sum filename The Red Hat security contact is security@redhat.com. More contact details at http://www.redhat.com/solutions/security/news/contact.html [***** End RHSA-2002:132-19 *****] _______________________________________________________________________________ CIAC wishes to acknowledge the contributions of Red Hat for the information contained in this bulletin. _______________________________________________________________________________ CIAC, the Computer Incident Advisory Capability, is the computer security incident response team for the U.S. Department of Energy (DOE) and the emergency backup response team for the National Institutes of Health (NIH). CIAC is located at the Lawrence Livermore National Laboratory in Livermore, California. CIAC is also a founding member of FIRST, the Forum of Incident Response and Security Teams, a global organization established to foster cooperation and coordination among computer security teams worldwide. CIAC services are available to DOE, DOE contractors, and the NIH. 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Neither the United States Government nor the University of California nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial products, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation or favoring by the United States Government or the University of California. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or the University of California, and shall not be used for advertising or product endorsement purposes. 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