IBM SECURITY ADVISORY

First Issued: Wed Dec  9 16:40:27 CST 2020

The most recent version of this document is available here:
http://aix.software.ibm.com/aix/efixes/security/ksu_advisory.asc
https://aix.software.ibm.com/aix/efixes/security/ksu_advisory.asc
ftp://aix.software.ibm.com/aix/efixes/security/ksu_advisory.asc

Security Bulletin: Vulnerability in ksu affects AIX (CVE-2020-4829)

===============================================================================

SUMMARY:

    There is a vulnerability in the ksu user command that affects AIX.


===============================================================================

VULNERABILITY DETAILS:

    CVEID: CVE-2020-4829
        http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2020-4829
        https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2020-4829
    DESCRIPTION: IBM AIX could allow a local user to exploit a vulnerability
        in the ksu user command to gain root privileges.
    CVSS Base Score: 8.4
    CVSS Temporal Score: See 
        https://exchange.xforce.ibmcloud.com/vulnerabilities/189960
        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:H/A:H)


    AFFECTED PRODUCTS AND VERSIONS:
 
        AIX 7.1, 7.2
        VIOS 3.1

        The following fileset levels are vulnerable:
        
        key_fileset = aix

        Fileset                 Lower Level  Upper Level KEY 
        ---------------------------------------------------------
        krb5.client.rte         1.16.1.0      1.16.1.2     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 krb5.client.rte


    REMEDIATION:

        FIXES

            AIX and VIOS fixes are available and can be downloaded from:

            https://www-01.ibm.com/marketing/iwm/iwm/web/pickUrxNew.do?source=aixbp

            To extract the fixes from the tar file:

            zcat NAS_1.16.1.3_aix_image.tar.Z | tar xvf -


            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 NAS_1.16.1.3_aix_image krb5

            To install the fix package:

            installp -aXYd NAS_1.16.1.3_aix_image krb5

 
            openssl dgst -sha1 -verify [pubkey_file] -signature [advisory_file].sig [advisory_file]
 
            openssl dgst -sha1 -verify [pubkey_file] -signature [ifix_file].sig [ifix_file]

            Published advisory OpenSSL signature file location:
 
            http://aix.software.ibm.com/aix/efixes/security/ksu_advisory.asc.sig
            https://aix.software.ibm.com/aix/efixes/security/ksu_advisory.asc.sig
            ftp://aix.software.ibm.com/aix/efixes/security/ksu_advisory.asc.sig 


    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

    To view previously issued advisories, please visit:

        http://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
    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: Vulnerability in ksu affects AIX (CVE-2020-4829)
        https://www.ibm.com/support/pages/node/6380430


ACKNOWLEDGEMENTS:

    None.


CHANGE HISTORY:

    First Issued: Wed Dec  9 16:40:27 CST 2020


===============================================================================

*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.