Vulnerabilities in OpenSSH affect AIX.

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
https://vulners.com/cve/CVE-2019-6109
https://vulners.com/cve/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
https://vulners.com/cve/CVE-2019-6110
https://vulners.com/cve/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
https://vulners.com/cve/CVE-2019-6111
https://vulners.com/cve/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
https://vulners.com/cve/CVE-2018-20685
https://vulners.com/cve/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.

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    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.