IBM SECURITY ADVISORY First Issued: Fri Jul 30 14:43:36 CDT 2021 |Updated: Wed Aug 11 14:52:54 CDT 2021 |Update: Corrected the AIX 7.1 TL5 affected fileset levels. The most recent version of this document is available here: http://aix.software.ibm.com/aix/efixes/security/ksh_advisory.asc https://aix.software.ibm.com/aix/efixes/security/ksh_advisory.asc ftp://aix.software.ibm.com/aix/efixes/security/ksh_advisory.asc Security Bulletin: Vulnerability in ksh affects AIX (CVE-2021-29741) =============================================================================== SUMMARY: There is a vulnerability in Korn Shell (ksh) that affects AIX. =============================================================================== VULNERABILITY DETAILS: CVEID: CVE-2021-29741 http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-29741 https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-29741 DESCRIPTION: IBM AIX could allow a local user to exploit a vulnerability in Korn Shell (ksh) to gain root privileges. CVSS Base Score: 8.4 CVSS Temporal Score: See https://exchange.xforce.ibmcloud.com/vulnerabilities/201478 for the current score CVSS Environmental Score*: Undefined CVSS Vector: (CVSS:3.0/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H) AFFECTED PRODUCTS AND VERSIONS: AIX 7.1, 7.2 VIOS 3.1 The vulnerabilities in the following filesets are being addressed: key_fileset = aix Fileset Lower Level Upper Level KEY --------------------------------------------------------- | bos.rte.shell 7.1.5.30 7.1.5.36 key_w_fs bos.rte.shell 7.2.3.0 7.2.3.20 key_w_fs bos.rte.shell 7.2.4.0 7.2.4.3 key_w_fs bos.rte.shell 7.2.5.0 7.2.5.2 key_w_fs To find out whether the affected filesets are installed on your systems, refer to the lslpp command found in AIX user's guide. Example: lslpp -L | grep -i bos.rte.shell REMEDIATION: A. APARS IBM has assigned the following APARs to this problem: AIX Level APAR Availability SP KEY ----------------------------------------------------- 7.1.5 IJ31606 ** SP09 key_w_apar 7.2.3 IJ32285 ** N/A key_w_apar 7.2.4 IJ31614 ** SP05 key_w_apar 7.2.5 IJ31545 ** SP03 key_w_apar VIOS Level APAR Availability SP KEY ---------------------------------------------------- 3.1.0 IJ32285 ** N/A key_w_apar 3.1.1 IJ31614 ** 3.1.1.50 key_w_apar 3.1.2 IJ30557 ** 3.1.2.30 key_w_apar Subscribe to the APARs here: http://www.ibm.com/support/pages/apar/IJ30557 http://www.ibm.com/support/pages/apar/IJ31545 http://www.ibm.com/support/pages/apar/IJ31606 http://www.ibm.com/support/pages/apar/IJ31614 http://www.ibm.com/support/pages/apar/IJ32285 https://www.ibm.com/support/pages/apar/IJ30557 https://www.ibm.com/support/pages/apar/IJ31545 https://www.ibm.com/support/pages/apar/IJ31606 https://www.ibm.com/support/pages/apar/IJ31614 https://www.ibm.com/support/pages/apar/IJ32285 By subscribing, you will receive periodic email alerting you to the status of the APAR, and a link to download the fix once it becomes available. B. FIXES AIX and VIOS fixes are available. The AIX and VIOS fixes can be downloaded via ftp or http from: ftp://aix.software.ibm.com/aix/efixes/security/ksh_fix.tar http://aix.software.ibm.com/aix/efixes/security/ksh_fix.tar https://aix.software.ibm.com/aix/efixes/security/ksh_fix.tar The link above is to a tar file containing this signed advisory, fix packages, and OpenSSL signatures for each package. The fixes below include prerequisite checking. This will enforce the correct mapping between the fixes and AIX Technology Levels. AIX Level Interim Fix (*.Z) KEY ---------------------------------------------- 7.1.5.6 IJ31606s6a.210628.epkg.Z key_w_fix 7.1.5.7 IJ31606s7a.210628.epkg.Z key_w_fix 7.1.5.8 IJ31606s7a.210628.epkg.Z key_w_fix 7.2.3.5 IJ32285s4a.210628.epkg.Z key_w_fix 7.2.3.6 IJ32285s4a.210628.epkg.Z key_w_fix 7.2.3.7 IJ32285s4a.210628.epkg.Z key_w_fix 7.2.4.2 IJ31614s1a.210427.epkg.Z key_w_fix 7.2.4.3 IJ31614s1a.210427.epkg.Z key_w_fix 7.2.4.4 IJ31614s1a.210427.epkg.Z key_w_fix 7.2.5.0 IJ30557s2a.210427.epkg.Z key_w_fix 7.2.5.1 IJ30557s2a.210427.epkg.Z key_w_fix 7.2.5.2 IJ30557s2a.210427.epkg.Z key_w_fix Please note that the above table refers to AIX TL/SP level as opposed to fileset level, i.e., 7.2.3.5 is AIX 7200-03-05. Please reference the Affected Products and Version section above for help with checking installed fileset levels. VIOS Level Interim Fix (*.Z) KEY ----------------------------------------------- 3.1.0.40 IJ32285s4a.210628.epkg.Z key_w_fix 3.1.0.50 IJ32285s4a.210628.epkg.Z key_w_fix 3.1.0.60 IJ32285s4a.210628.epkg.Z key_w_fix 3.1.1.20 IJ31614s1a.210427.epkg.Z key_w_fix 3.1.1.21 IJ31614s1a.210427.epkg.Z key_w_fix 3.1.1.25 IJ31614s1a.210427.epkg.Z key_w_fix 3.1.1.30 IJ31614s1a.210427.epkg.Z key_w_fix 3.1.1.40 IJ31614s1a.210427.epkg.Z key_w_fix 3.1.2.0 IJ30557s2a.210427.epkg.Z key_w_fix 3.1.2.10 IJ30557s2a.210427.epkg.Z key_w_fix 3.1.2.20 IJ30557s2a.210427.epkg.Z key_w_fix 3.1.2.21 IJ30557s2a.210427.epkg.Z key_w_fix To extract the fixes from the tar file: tar xvf ksh_fix.tar cd ksh_fix Verify you have retrieved the fixes intact: The checksums below were generated using the "openssl dgst -sha256 [filename]" command as the following: openssl dgst -sha256 filename KEY ----------------------------------------------------------------------------------------------------- 937c07cf9e42f7d0a5f2c4d3deee84da46bef49c174ffeb8d01f010d5aacd11e IJ30557s2a.210427.epkg.Z key_w_csum 764dfe4293c05298cc7325d57106850382a341127bbd9a0fefb469ff42706aa8 IJ31606s6a.210628.epkg.Z key_w_csum de26cdab804af608be1392c53346037d7cd2de91cf67acab5d0e9d3ca988763a IJ31606s7a.210628.epkg.Z key_w_csum 2e9acbabe8632065096fe4e1ea6387af23cb495bff8e744c91205ba280bfa855 IJ31614s1a.210427.epkg.Z key_w_csum 6e7efc563989dc3a504ae9626b36053d2d58a6f3242660830c5019d67953dfa7 IJ32285s4a.210628.epkg.Z key_w_csum These sums should match exactly. The OpenSSL signatures in the tar file and on this advisory can also be used to verify the integrity of the fixes. If the sums or signatures cannot be confirmed, contact IBM Support at http://ibm.com/support/ and describe the discrepancy. openssl dgst -sha256 -verify [pubkey_file] -signature [advisory_file].sig [advisory_file] openssl dgst -sha256 -verify [pubkey_file] -signature [ifix_file].sig [ifix_file] Published advisory OpenSSL signature file location: http://aix.software.ibm.com/aix/efixes/security/ksh_advisory.asc.sig https://aix.software.ibm.com/aix/efixes/security/ksh_advisory.asc.sig ftp://aix.software.ibm.com/aix/efixes/security/ksh_advisory.asc.sig C. FIX AND INTERIM FIX INSTALLATION If possible, it is recommended that a mksysb backup of the system be created. Verify it is both bootable and readable before proceeding. To preview a fix installation: installp -a -d fix_name -p all # where fix_name is the name of the # fix package being previewed. To install a fix package: installp -a -d fix_name -X all # where fix_name is the name of the # fix package being installed. Interim fixes have had limited functional and regression testing but not the full regression testing that takes place for Service Packs; however, IBM does fully support them. Interim fix management documentation can be found at: http://www14.software.ibm.com/webapp/set2/sas/f/aix.efixmgmt/home.html To preview an interim fix installation: emgr -e ipkg_name -p # where ipkg_name is the name of the # interim fix package being previewed. To install an interim fix package: emgr -e ipkg_name -X # where ipkg_name is the name of the # interim fix package being installed. WORKAROUNDS AND MITIGATIONS: None. =============================================================================== CONTACT US: Note: Keywords labeled as KEY in this document are used for parsing purposes. If you would like to receive AIX Security Advisories via email, please visit "My Notifications": http://www.ibm.com/support/mynotifications To view previously issued advisories, please visit: http://www14.software.ibm.com/webapp/set2/subscriptions/onvdq Contact IBM Support for questions related to this announcement: http://ibm.com/support/ https://ibm.com/support/ To obtain the OpenSSL public key that can be used to verify the signed advisories and ifixes: Download the key from our web page: ftp://ftp.software.ibm.com/systems/power/AIX/systems_p_os_aix_security_pubkey.txt Please contact your local IBM AIX support center for any assistance. REFERENCES: Complete CVSS v3 Guide: http://www.first.org/cvss/user-guide On-line Calculator v3: http://www.first.org/cvss/calculator/3.0 RELATED INFORMATION: IBM Secure Engineering Web Portal http://www.ibm.com/security/secure-engineering/bulletins.html IBM Product Security Incident Response Blog https://www.ibm.com/blogs/psirt/ Security Bulletin: Vulnerability in ksh affects AIX (CVE-2021-29741) https://www.ibm.com/support/pages/node/6477018 ACKNOWLEDGEMENTS: None. CHANGE HISTORY: First Issued: Fri Jul 30 14:43:36 CDT 2021 | Updated: Wed Aug 11 14:52:54 CDT 2021 | Update: Corrected the AIX 7.1 TL5 affected fileset levels. =============================================================================== *The CVSS Environment Score is customer environment specific and will ultimately impact the Overall CVSS Score. Customers can evaluate the impact of this vulnerability in their environments by accessing the links in the Reference section of this Security Bulletin. Disclaimer According to the Forum of Incident Response and Security Teams (FIRST), the Common Vulnerability Scoring System (CVSS) is an "industry open standard designed to convey vulnerability severity and help to determine urgency and priority of response." IBM PROVIDES THE CVSS SCORES "AS IS" WITHOUT WARRANTY OF ANY KIND, INCLUDING THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. CUSTOMERS ARE RESPONSIBLE FOR ASSESSING THE IMPACT OF ANY ACTUAL OR POTENTIAL SECURITY VULNERABILITY.