IBM SECURITY ADVISORY First Issued: Thu Jan 6 09:17:41 CST 2022 The most recent version of this document is available here: http://aix.software.ibm.com/aix/efixes/security/openssh_advisory14.asc https://aix.software.ibm.com/aix/efixes/security/openssh_advisory14.asc ftp://aix.software.ibm.com/aix/efixes/security/openssh_advisory14.asc Security Bulletin: Vulnerability in OpenSSH affects AIX (CVE-2021-41617) =============================================================================== SUMMARY: There is a vulnerability in OpenSSH used by AIX. =============================================================================== VULNERABILITY DETAILS: CVEID: CVE-2021-41617 http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-41617 https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-41617 DESCRIPTION: OpenSSH could allow a local attacker to gain elevated privileges on the system, caused by an error in sshd when certain non-default configurations are used. By executing an AuthorizedKeysCommand or AuthorizedPrincipalsCommand, where a AuthorizedKeysCommandUser or AuthorizedPrincipalsCommandUser directive has been set to run the command as a non-root user, an attacker could exploit this vulnerability to gain privileges associated with group memberships of the sshd process. CVSS Base Score: 7.4 CVSS Temporal Score: See https://exchange.xforce.ibmcloud.com/vulnerabilities/210062 for the current score CVSS Environmental Score*: Undefined CVSS Vector:(CVSS:3.0/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H) AFFECTED PRODUCTS AND VERSIONS: AIX 7.1, 7.2, 7.3 VIOS 3.1 The following fileset levels are vulnerable: key_fileset = osrcaix Fileset Lower Level Upper Level KEY ------------------------------------------------------------- openssh.base.client 8.1.102.2000 8.1.102.2104 key_w_fs openssh.base.server 8.1.102.2000 8.1.102.2104 key_w_fs Note: A. 6.0, 7.1, 7.5 OpenSSH versions are out-of-support. Refer to AIX release notes for supported OpenSSH versions. Customers are advised to upgrade to currently supported OpenSSH 8.1 version. B. Latest level of OpenSSH fileset is available from the web download site: https://www.ibm.com/resources/mrs/assets?source=aixbp&S_PKG=openssh To determine if your system is vulnerable, execute the following commands: lslpp -L | grep -i openssh.base.client lslpp -L | grep -i openssh.base.server REMEDIATION: A. FIXES The fixes can be downloaded via ftp or http from: ftp://aix.software.ibm.com/aix/efixes/security/openssh_fix14.tar http://aix.software.ibm.com/aix/efixes/security/openssh_fix14.tar https://aix.software.ibm.com/aix/efixes/security/openssh_fix14.tar The links above are 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. Note that the tar file contains Interim fixes that are based on OpenSSL version, and AIX OpenSSL fixes are cumulative. You must be on the 'prereq for installation' level before applying the interim fix. This may require installing a new level(prereq version) first. AIX Level Interim Fix (*.Z) Fileset Name(prereq for installation) KEY --------------------------------------------------------------------------------------- 7.1, 7.2 41617s9a.211029.epkg.Z openssh.base(8.1.102.2103) key_w_fix VIOS Level Interim Fix (*.Z) Fileset Name(prereq for installation) KEY -------------------------------------------------------------------------------------------- 3.1.x 41617s9a.211029.epkg.Z openssh.base(8.1.102.2103) key_w_fix To extract the fixes from the tar file: tar xvf openssh_fix14.tar cd openssh_fix14 Verify you have retrieved the fixes intact: The checksums below were generated using the "openssl dgst -sha256 [file]" command as the following: openssl dgst -sha256 filename KEY ----------------------------------------------------------------------------------------------------- 1d134a4f95413d2e79ac5e9d577692602295cf524e9611916987b478a5b0d547 41617s9a.211029.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 AIX Support at https://ibm.com/support/ and describe the discrepancy. openssl dgst -sha256 -verify -signature .sig openssl dgst -sha256 -verify -signature .sig Published advisory OpenSSL signature file location: http://aix.software.ibm.com/aix/efixes/security/openssh_advisory14.asc.sig https://aix.software.ibm.com/aix/efixes/security/openssh_advisory14.asc.sig ftp://aix.software.ibm.com/aix/efixes/security/openssh_advisory14.asc.sig B. FIX AND INTERIM FIX INSTALLATION 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 https://www.ibm.com/support/mynotifications To view previously issued advisories, please visit: http://www14.software.ibm.com/webapp/set2/subscriptions/onvdq https://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 https://www.first.org/cvss/user-guide On-line Calculator v3: http://www.first.org/cvss/calculator/3.0 https://www.first.org/cvss/calculator/3.0 RELATED INFORMATION: Security Bulletin: Vulnerability in OpenSSH affects AIX (CVE-2021-41617) https://www.ibm.com/support/pages/node/6538690 ACKNOWLEDGEMENTS: None. CHANGE HISTORY: First Issued: Thu Jan 6 09:17:41 CST 2022 =============================================================================== *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.