IBM SECURITY ADVISORY First Issued: Wed Oct 24 11:28:50 CDT 2018 The most recent version of this document is available here: http://aix.software.ibm.com/aix/efixes/security/openssh_advisory12.asc https://aix.software.ibm.com/aix/efixes/security/openssh_advisory12.asc ftp://aix.software.ibm.com/aix/efixes/security/openssh_advisory12.asc Security Bulletin: Vulnerability in OpenSSH affects AIX (CVE-2018-15473) =============================================================================== SUMMARY: Vulnerability in OpenSSH affects AIX. =============================================================================== VULNERABILITY DETAILS: CVEID: CVE-2018-15473 http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2018-15473 https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2018-15473 DESCRIPTION: OpenSSH could allow a remote attacker to obtain sensitive information, caused by different responses to valid and invalid authentication attempts. By sending a specially crafted request, an attacker could exploit this vulnerability to enumerate valid usernames. CVSS Base Score: 5.3 CVSS Temporal Score: See https://exchange.xforce.ibmcloud.com/vulnerabilities/148397 for the current score. CVSS Environmental Score*: Undefined CVSS Vector: (CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N) AFFECTED PRODUCTS AND VERSION: AIX 5.3, 6.1, 7.1, 7.2 VIOS 2.2.x The following fileset levels are vulnerable: key_fileset = osrcaix Fileset Lower Level Upper Level KEY ------------------------------------------------------------- openssh.base.client 4.0.0.5200 7.5.102.1500 key_w_fs openssh.base.server 4.0.0.5200 7.5.102.1500 key_w_fs Note: 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 Fixes are available. The fixes can be downloaded via ftp and http from: ftp://aix.software.ibm.com/aix/efixes/security/openssh_fix12.tar http://aix.software.ibm.com/aix/efixes/security/openssh_fix12.tar https://aix.software.ibm.com/aix/efixes/security/openssh_fix12.tar The links above are to a tar file containing this signed advisory, interim fixes, and OpenSSL signatures for each interim fix. These fixes below include prerequisite checking. This will enforce the correct mapping between the fixes and AIX releases. Note that the tar file contains Interim fixes that are based on OpenSSH version as given below. 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 --------------------------------------------------------------------------------------------- 5.3, 6.1, 7.1, 7.2 15473_fix.180919.epkg.Z openssh.base (7.5.102.1500 version) key_w_fix VIOS Level Interim Fix (*.Z) Fileset Name (prereq for installation) KEY --------------------------------------------------------------------------------------------- 2.2.x 15473_fix.180919.epkg.Z openssh.base (7.5.102.1500 version) key_w_fix Latest level of OpenSSH fileset is available from the web download site: https://www14.software.ibm.com/webapp/iwm/web/reg/download.do?source=aixbp&lang=en_US&S_PKG=openssh&cp=UTF-8 To extract the fix from the tar file: tar xvf openssh_fix12.tar cd openssh_fix12 Verify you have retrieved the fix intact: The checksums below were generated using the "openssl dgst -sha256 file" command is the following: openssl dgst -sha256 filename KEY ----------------------------------------------------------------------------------------------------- 45ac81fc8766c41a7244ec2481ffa38aa90ca1b7c99b0b0acb1e4d82826b842a 15473_fix.180919.epkg.Z key_w_csum Published advisory OpenSSH signature file location: http://aix.software.ibm.com/aix/efixes/security/openssh_advisory12.asc.sig https://aix.software.ibm.com/aix/efixes/security/openssh_advisory12.asc.sig ftp://aix.software.ibm.com/aix/efixes/security/openssh_advisory12.asc.sig openssl dgst -sha1 -verify [pubkey_file] -signature [advisory_file].sig [advisory_file] openssl dgst -sha1 -verify [pubkey_file] -signature [ifix_file].sig [ifix_file] B. FIX AND INTERIM FIX INSTALLATION After applying fix, IBM recommends that you regenerate your SSH keys as a precaution. IMPORTANT: 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 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-2018-15473) https://www-01.ibm.com/support/docview.wss?uid=ibm10733751 ACKNOWLEDGEMENTS: None CHANGE HISTORY: First Issued: Wed Oct 24 11:28:50 CDT 2018 =============================================================================== *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 Flash. Note: 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.