IBM SECURITY ADVISORY First Issued: Tue Jul 16 09:38:57 CDT 2019 The most recent version of this document is available here: http://aix.software.ibm.com/aix/efixes/security/openssh_advisory13.asc https://aix.software.ibm.com/aix/efixes/security/openssh_advisory13.asc ftp://aix.software.ibm.com/aix/efixes/security/openssh_advisory13.asc Security Bulletin: Vulnerabilities in OpenSSH affect AIX (CVE-2018-20685 CVE-2018-6109 CVE-2018-6110 CVE-2018-6111) =============================================================================== SUMMARY: Vulnerabilities in OpenSSH affect AIX. =============================================================================== VULNERABILITY DETAILS: CVEID: CVE-2019-6109 http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2019-6109 https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2019-6109 DESCRIPTION: OpenSSH could allow a remote attacker to conduct spoofing attacks, caused by missing character encoding in the progress display. A man-in-the-middle attacker could exploit this vulnerability to spoof scp client output. CVSS Base Score: 3.1 CVSS Temporal Score: See https://exchange.xforce.ibmcloud.com/vulnerabilities/155488 for the current score. CVSS Environmental Score*: Undefined CVSS Vector: (CVSS:3.0/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:L/A:N) CVEID: CVE-2019-6110 http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2019-6110 https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2019-6110 DESCRIPTION: OpenSSH could allow a remote attacker to conduct spoofing attacks, caused by accepting and displaying arbitrary stderr output from the scp server. A man-in-the-middle attacker could exploit this vulnerability to spoof scp client output. CVSS Base Score: 3.1 CVSS Temporal Score: See https://exchange.xforce.ibmcloud.com/vulnerabilities/155487 for the current score. CVSS Environmental Score*: Undefined CVSS Vector: (CVSS:3.0/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:L/A:N) CVEID: CVE-2019-6111 http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2019-6111 https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2019-6111 DESCRIPTION: OpenSSH could allow a remote attacker to overwrite arbitrary files on the system, caused by missing received object name validation by the scp client. The scp implementation accepts arbitrary files sent by the server and a man-in-the-middle attacker could exploit this vulnerability to overwrite unrelated files. CVSS Base Score: 5.3 CVSS Temporal Score: See https://exchange.xforce.ibmcloud.com/vulnerabilities/155486 for the current score. CVSS Environmental Score*: Undefined CVSS Vector: (CVSS:3.0/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:H/A:N) CVEID: CVE-2018-20685 http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2018-20685 https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2018-20685 DESCRIPTION: In OpenSSH 7.9, scp.c in the scp client allows remote SSH servers to bypass intended access restrictions via the filename of . or an empty filename. The impact is modifying the permissions of the target directory on the client side. CVSS Base Score: 7.5 CVSS Temporal Score: See https://exchange.xforce.ibmcloud.com/vulnerabilities/155484 for the current score. CVSS Environmental Score*: Undefined CVSS Vector: (CVSS:3.0/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H) AFFECTED PRODUCTS AND VERSION: AIX 7.1, 7.2 VIOS 2.2, 3.1 The following fileset levels are vulnerable: key_fileset = osrcaix Fileset Lower Level Upper Level KEY ------------------------------------------------------------- openssh.base.client 4.0.0.5200 7.5.102.1600 key_w_fs openssh.base.server 4.0.0.5200 7.5.102.1600 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: FIXES A fix is available for CVE-2018-20685, CVE-2019-6109, and CVE-2019-6111, and it can be downloaded from: https://www-01.ibm.com/marketing/iwm/iwm/web/pickUrxNew.do?source=aixbp&S_PKG=openssh Please see the WORKAROUNDS AND MITIGATIONS section for mitigation steps in response to CVE-2019-6110. To extract the fixes from the tar file: For Openssh 7.5 version - zcat openssh-7.5.102.1800.tar.Z | tar xvf Please refer to the Readme file to be aware of the changes that are part of the release. IMPORTANT: If possible, it is recommended that a mksysb backup of the system be created. Verify it is both bootable and readable before proceeding. Note that all the previously reported security vulnerability fixes are also included in above mentioned fileset level. Please refer to the readme file (provided along with the fileset) for the complete list of vulnerabilities fixed. To preview the fix installation: installp -apYd . openssh To install the fix package: installp -aXYd . openssh Published advisory OpenSSH signature file location: http://aix.software.ibm.com/aix/efixes/security/openssh_advisory13.asc.sig https://aix.software.ibm.com/aix/efixes/security/openssh_advisory13.asc.sig ftp://aix.software.ibm.com/aix/efixes/security/openssh_advisory13.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] WORKAROUNDS AND MITIGATIONS: The potential impact of CVE-2019-6110 may be mitigated by using the sftp command in place of the scp command. =============================================================================== 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: 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: Vulnerabilities in OpenSSH affect AIX https://www-01.ibm.com/support/docview.wss?uid=ibm10872060 ACKNOWLEDGEMENTS: None. CHANGE HISTORY: First Issued: Tue Jul 16 09:38:57 CDT 2019 =============================================================================== *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.