Vulnerabilities in OpenSSH affect AIX.

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
https://vulners.com/cve/CVE-2018-15473
https://vulners.com/cve/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:

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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.