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-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 =========================================================================== AUSCERT External Security Bulletin Redistribution ESB-2007.0612 -- [AIX] AIX at Command Buffer Overflow Vulnerability 13 August 2007 =========================================================================== AusCERT Security Bulletin Summary --------------------------------- Product: at Publisher: IBM Operating System: AIX 5.2 AIX 5.3 Impact: Root Compromise Access: Existing Account - --------------------------BEGIN INCLUDED TEXT-------------------- - -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 IBM SECURITY ADVISORY First Issued: Tue Aug 7 17:42:20 CDT 2007 =============================================================================== VULNERABILITY SUMMARY VULNERABILITY: AIX at Command Buffer Overflow Vulnerability PLATFORMS: AIX 5.3 SOLUTION: Apply the APAR, interim fix or workaround as described below. THREAT: An attacker may run arbitrary code with root privileges. CERT VU Number: n/a CVE Number: n/a =============================================================================== DETAILED INFORMATION I. OVERVIEW The 'at' command reads from standard input the names of commands to be run at a later time and allows you to specify when the commands should be run. II. DESCRIPTION A buffer overflow vulnerability exists in the at command whereby a local user may execute arbitrary code with root privileges. III. IMPACT The successful exploitation of this vulnerability allows a non-privileged user to execute code with root privileges. IV. PLATFORM VULNERABILITY ASSESSMENT To determine if your system is vulnerable, run the following command: # lslpp -l | grep bos.rte.cron The following filesets levels are vulnerable: AIX Level Lower Level Upper Level ------------------------------------------------- 5.3.0 5.3.0.0 5.3.0.60 NOTE: IBM only supports the latest two releases (AIX 5.2 & 5.3) and the latest three Technology Levels (AIX 5.2 TL08, TL09, TL10 & AIX 5.3 TL04, TL05, TL06). Affected customers are urged to upgrade to the latest applicable Technology Level and Service Pack. V. SOLUTIONS A. APARS IBM provides the following fixes: AIX Level APAR number Availability -------------------------------------------------------------------- 5.3.0 IZ00139 Available AIX Version 5 APARs can be downloaded from: http://www.ibm.com/servers/eserver/support/unixservers/aixfixes.html NOTE: Affected customers are urged to upgrade to the latest applicable Technology Level and Service Pack. B. INTERIM FIXES Interim fixes are available. The interim fix can be downloaded via ftp from: ftp://aix.software.ibm.com/aix/efixes/security/at_ifix.tar.Z This is a compressed tarball containing this advisory, interim fix packages and PGP signatures for each package. The interim fixes below include prerequisite checking. This will enforce the correct mapping between the fixes and AIX Technology Levels. AIX Release & Technology Level Interim fix --------------------------------------------------------------- 5300-04 IZ00139_04.070614.epkg.Z 5300-05 IZ00139_05.070614.epkg.Z 5300-06 IZ00139_06.070618.epkg.Z IMPORTANT: If possible, it is recommended that a mksysb backup of the system be created. Verify it is both bootable and readable before proceeding. These interim fixes have not been fully regression tested; thus, IBM does not warrant the fully correct functionality of the interim fix. Customers install the interim fix and operate the modified version of AIX at their own risk. Verify you have retrieved the fixes intact: The interim fixes below are named by using the technology level corresponding to the release that the fix applies to. The checksums below were generated using the "sum" and "md5sum" commands and are as follows: Filename sum md5sum ---------------------------------------------------------------------- IZ00139_04.070614.epkg.Z 48571 93 846844e63c1a448839b671d6387cca30 IZ00139_05.070614.epkg.Z 43020 94 1b8f331215ecc7ba5b65ec046b0cd003 IZ00139_06.070618.epkg.Z 19174 94 0d8ee47181c7b74454ad0331cea9a57b These sums should match exactly. The PGP signatures in the compressed tarball and on this advisory can also be used to verify the integrity of the various files they correspond to. If the sums or signatures cannot be confirmed, double check the command results and the download site address. If those are OK, contact IBM AIX Security at security-alert@austin.ibm.com and describe the discrepancy. C. INTERIM FIX INSTALLATION These packages use the new Interim Fix Management Solution to install and manage interim fixes. More information can be found at: http://www14.software.ibm.com/webapp/set2/sas/f/aix.efixmgmt/home.html To preview an epkg interim fix installation execute the following command: # emgr -e ipkg_name -p # where ipkg_name is the name of the # interim fix package being previewed. To install an epkg interim fix package, execute the following command: # emgr -e ipkg_name -X # where ipkg_name is the name of the # interim fix package being installed. The "X" flag will expand any filesystems if required. VI. WORKAROUNDS There are a couple of workarounds that may be implemented. A. OPTION 1 If the program is unnecessary, it may be removed with the following command: # rm -f /usr/bin/at NOTE: To restore this command, the entire bos.rte.cron package must be reinstalled. B. OPTION 2 Change the permissions of this command to remove the setuid bit using the following command: # chmod 500 /usr/bin/at NOTE: This will disable functionality of the command for all users except root. C. OPTION 3 Customers running AIX 5.3.0 TL06 may install the bos.rte.security fileset and take advantage of the 'fpm' command to disable the setuid capabilities of many SUID commands. The 'at' command is addressed in the high fpm database. D. OPTION 4 Stack execution disable may be enabled on machines running AIX 5.3 TL05 or later. VII. OBTAINING FIXES AIX Version 5 APARs can be downloaded from: http://www.ibm.com/servers/eserver/support/unixservers/aixfixes.html Security related Interim Fixes can be downloaded from: ftp://aix.software.ibm.com/aix/efixes/security VII. CONTACT INFORMATION If you would like to receive AIX Security Advisories via email, please visit: http://www14.software.ibm.com/webapp/set2/subscriptions/pqvcmjd Comments regarding the content of this announcement can be directed to: security-alert@austin.ibm.com To request the PGP public key that can be used to communicate securely with the AIX Security Team you can either: A. Send an email with "get key" in the subject line to: security-alert@austin.ibm.com B. Download the key from a PGP Public Key Server. The key ID is: 0x4265D862 Please contact your local IBM AIX support center for any assistance. eServer is a trademark of International Business Machines Corporation. IBM, AIX and pSeries are registered trademarks of International Business Machines Corporation. All other trademarks are property of their respective holders. VIII. ACKNOWLEDGMENTS This vulnerability was discovered internal to IBM as part of its commitment to secure the AIX operating system. - -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.7 (AIX) iD8DBQFGuPWZ0eNzcEJl2GIRAoKcAKCEfFRZ8K1fKEyZKRaZ17Wwl4PHtgCgk6Ul PtxepwnRDGV2R6VsWHxYXLI= =XRoJ - -----END PGP SIGNATURE----- - --------------------------END INCLUDED TEXT-------------------- You have received this e-mail bulletin as a result of your organisation's registration with AusCERT. The mailing list you are subscribed to is maintained within your organisation, so if you do not wish to continue receiving these bulletins you should contact your local IT manager. If you do not know who that is, please send an email to auscert@auscert.org.au and we will forward your request to the appropriate person. NOTE: Third Party Rights This security bulletin is provided as a service to AusCERT's members. As AusCERT did not write the document quoted above, AusCERT has had no control over its content. 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Previous advisories and external security bulletins can be retrieved from: http://www.auscert.org.au/render.html?cid=1980 If you believe that your computer system has been compromised or attacked in any way, we encourage you to let us know by completing the secure National IT Incident Reporting Form at: http://www.auscert.org.au/render.html?it=3192 =========================================================================== Australian Computer Emergency Response Team The University of Queensland Brisbane Qld 4072 Internet Email: auscert@auscert.org.au Facsimile: (07) 3365 7031 Telephone: (07) 3365 4417 (International: +61 7 3365 4417) AusCERT personnel answer during Queensland business hours which are GMT+10:00 (AEST). On call after hours for member emergencies only. =========================================================================== -----BEGIN PGP SIGNATURE----- Comment: http://www.auscert.org.au/render.html?it=1967 iQCVAwUBRr/DYyh9+71yA2DNAQJoQwQAjDouVoRfWWbPBt5H5+BJfgm6rP+CI+Aq Wc8hChr7qxzjKHGtDFBJLjm9RPWTJKYHGKBaar2RnfVYEf1WywlG/VE3kHNAXg+/ u4Gs9IEZC7Fgx4JPef521lF99/7AV3/j4ZZammrIzSDHiFpJ1egkohNBK6u7YRnk +xJexlDljrY= =wwhT -----END PGP SIGNATURE-----