IBM SECURITY ADVISORY First Issued: Wed Aug 23 08:36:37 CDT 2023 The most recent version of this document is available here: https://aix.software.ibm.com/aix/efixes/security/openssh_advisory15.asc Security Bulletin: AIX is vulnerable to unauthorized file access and arbitrary code execution due to OpenSSH (CVE-2023-40371 and CVE-2023-38408) =============================================================================== SUMMARY: Vulnerabilities in AIX's OpenSSH could allow a non-privileged local user file access outside of those allowed (CVE-2023-40371) or allow a remote attacker to execute arbitrary code (CVE-2023-38408). OpenSSH is used by AIX for remote login. =============================================================================== VULNERABILITY DETAILS: CVEID: CVE-2023-40371 https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2023-40371 DESCRIPTION: IBM AIX's OpenSSH implementation could allow a non-privileged local user to access files outside of those allowed due to improper access controls. CVSS Base Score: 6.2 CVSS Temporal Score: See https://exchange.xforce.ibmcloud.com/vulnerabilities/263476 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:N/A:N) CVEID: CVE-2023-38408 https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2023-38408 DESCRIPTION: OpenSSH could allow a remote attacker to execute arbitrary code on the system, caused by a flaw in the forwarded ssh-agent. By sending specially crafted requests, an attacker could exploit this vulnerability to execute arbitrary code on the system. CVSS Base Score: 8.1 CVSS Temporal Score: See https://exchange.xforce.ibmcloud.com/vulnerabilities/261022 for the current score CVSS Environmental Score*: Undefined CVSS Vector: (CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H) AFFECTED PRODUCTS AND VERSIONS: AIX 7.2, 7.3 VIOS 3.1 The following fileset levels are vulnerable: key_fileset = aix Fileset Lower Level Upper Level KEY ---------------------------------------------------------- openssh.base.client 8.1.102.0 8.1.102.2106 key_w_fs openssh.base.server 8.1.102.0 8.1.102.2106 key_w_fs openssh.base.client 8.1.112.0 8.1.112.2000 key_w_fs openssh.base.server 8.1.112.0 8.1.112.2000 key_w_fs openssh.base.client 9.2.112.0 9.2.112.2000 key_w_fs openssh.base.server 9.2.112.0 9.2.112.2000 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 openssh.base.client REMEDIATION: A. FIXES IBM strongly recommends addressing the vulnerability now. AIX and VIOS fixes are available. The AIX and VIOS fixes can be downloaded via https from: https://aix.software.ibm.com/aix/efixes/security/openssh_fix15.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. Note that the tar file contains Interim fixes that are based on OpenSSH version, and AIX OpenSSH 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 from: https://www.ibm.com/resources/mrs/assets?source=aixbp AIX Level Interim Fix (*.Z) Fileset Name(prereq for installation) KEY --------------------------------------------------------------------------------------- 7.2, 7.3 38408m9a.230811.epkg.Z openssh.base(8.1.102.2106) key_w_fix 7.2, 7.3 38408m9b.230811.epkg.Z openssh.base(8.1.112.2000) key_w_fix 7.2, 7.3 38408m9c.230811.epkg.Z openssh.base(9.2.112.2000) key_w_fix VIOS Level Interim Fix (*.Z) Fileset Name(prereq for installation) KEY -------------------------------------------------------------------------------------------- 3.1 38408m9a.230811.epkg.Z openssh.base(8.1.102.2106) key_w_fix 3.1 38408m9b.230811.epkg.Z openssh.base(8.1.112.2000) key_w_fix 3.1 38408m9c.230811.epkg.Z openssh.base(9.2.112.2000) key_w_fix To extract the fixes from the tar file: tar xvf openssh_fix15.tar cd openssh_fix15 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 ----------------------------------------------------------------------------------------------------- 77dbc3b40635e16a2f9dba178727bc3fd5e3321c36823c147eb878250e7f6fd0 38408m9a.230811.epkg.Z key_w_csum 7a4f56811b3dc179916d5b6de337d40775904f2718480d94dc5a97cd92dc4a25 38408m9b.230811.epkg.Z key_w_csum 873adbb99a01500b60729c12bf9a9c18ccf0ac74902cb051d5288eeb4f6ad168 38408m9c.230811.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: https://aix.software.ibm.com/aix/efixes/security/openssh_advisory15.asc.sig B. 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 Contact IBM Support for questions related to this announcement: https://ibm.com/support/ For information on how to securely verify AIX security bulletins and fixes: https://www.ibm.com/support/pages/node/6985269 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 https://aix.software.ibm.com/aix/efixes/security/systems_p_os_aix_security_pubkey.txt To verify the AIX/VIOS security bulletin: Published advisory OpenSSL signature file location: https://aix.software.ibm.com/aix/efixes/security/openssh_advisory15.asc.sig openssl dgst -sha256 -verify [pubkey_file] -signature [advisory_file].sig [advisory_file] 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: AIX is vulnerable to unauthorized file access and arbitrary code execution due to OpenSSH (CVE-2023-40371 and CVE-2023-38408) https://www.ibm.com/support/pages/node/7028420 ACKNOWLEDGEMENTS: None. CHANGE HISTORY: First Issued: Wed Aug 23 08:36:37 CDT 2023 =============================================================================== *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.