AIX is vulnerable to denial of service due to zlib and zlibNX

IBM SECURITY ADVISORY

First Issued: Tue Jul 25 11:05:17 CDT 2023

The most recent version of this document is available here:
https://aix.software.ibm.com/aix/efixes/security/zlib_advisory2.asc

Security Bulletin: AIX is vulnerable to denial of service due to zlib
(CVE-2022-37434)

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

SUMMARY:

A vulnerability in zlib and zlibNX could allow a remote attacker to cause
a denial of service (CVE-2022-37434). AIX uses zlib and zlibNX as part 
of its data compression functions.

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

VULNERABILITY DETAILS:

CVEID: CVE-2022-37434
    https://vulners.com/cve/CVE-2022-37434
DESCRIPTION: zlib is vulnerable to a heap-based buffer overflow, caused by
    improper bounds checking by inflate in inflate.c. By using a large
    gzip header extra field, a remote attacker could overflow a buffer and
    execute arbitrary code on the system.
CVSS Base Score: 7.3
CVSS Temporal Score: See 
    https://exchange.xforce.ibmcloud.com/vulnerabilities/232849
    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:L/A:L)


AFFECTED PRODUCTS AND VERSIONS:

    AIX 7.1, 7.2, 7.3
    VIOS 3.1

    The following fileset levels are vulnerable:
    
    key_fileset = aix

    For zlib:

    Fileset                 Lower Level  Upper Level KEY       PRODUCT(S)
    ---------------------------------------------------------------------
    rpm.rte                 4.9.1.3      4.15.1.1006 key_w_fs  zlib
    rpm.rte                 4.15.1.2000  4.15.1.2006 key_w_fs  zlib

    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 rpm.rte


    For zlibNX:

    Fileset                 Lower Level  Upper Level KEY       PRODUCT(S)
    ---------------------------------------------------------------------
    zlibNX.rte              7.2.4.0      7.2.4.8     key_w_fs  zlibNX
    zlibNX.rte              7.3.0.0      7.3.0.2     key_w_fs  zlibNX
    zlibNX.rte              7.3.1.0      7.3.1.0     key_w_fs  zlibNX

    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 zlibNX.rte


REMEDIATION:

    A. FIXES

        IBM strongly recommends addressing the vulnerability now.

        AIX and VIOS fixes are available. The fixes are cumulative and
        address previously issued AIX/VIOS zlib security bulletins with
        respect to SP and TL.

        The AIX and VIOS fixes can be downloaded via https from:

        https://aix.software.ibm.com/aix/efixes/security/zlib_fix2.tar 

        The link above is to a tar file containing this signed
        advisory, fix packages, and OpenSSL signatures for each package.
        The fixes below include prerequisite checking. This will
        enforce the correct mapping between the fixes and AIX
        Technology Levels.

        For zlib:

        AIX Level       Fix                       KEY        PRODUCT(S)
        ---------------------------------------------------------------
        7.2             rpm.rte.4.15.1.1007       key_w_fix  zlib
        7.3             rpm.rte.4.15.1.2007       key_w_fix  zlib

        VIOS Level      Fix                       KEY        PRODUCT(S)
        ---------------------------------------------------------------
        3.1             rpm.rte.4.15.1.1007       key_w_fix  zlib


        For zlibNX:

        AIX Level  Interim Fix (*.Z)         KEY        PRODUCT(S)
        ----------------------------------------------------------
        7.2.5      IJ47324m5a.230623.epkg.Z  key_w_fix  zlibNX
        7.3.0      IJ46030m3a.230623.epkg.Z  key_w_fix  zlibNX
        7.3.1      IJ44986s1a.230623.epkg.Z  key_w_fix  zlibNX

        Please reference the Affected Products and Version section above
        for help with checking installed fileset levels.

        VIOS Level  Interim Fix (*.Z)         KEY        PRODUCT(S)
        -----------------------------------------------------------
        3.1         IJ47324m5a.230623.epkg.Z  key_w_fix  zlibNX


        To extract the fixes from the tar file:

        tar xvf zlib_fix2.tar
        cd zlib_fix2

        Verify you have retrieved the fixes intact:

        The checksums below were generated using the
        "openssl dgst -sha256 [filename]" command as the following:

        openssl dgst -sha256                                              filename                 KEY
        -----------------------------------------------------------------------------------------------------
        66c4bf4452aa9d6aa7fdb13adc150712449ed679a7e5a09cc83eeaf54135acc9  IJ44986s1a.230623.epkg.Z key_w_csum
        8b49543d3af33b8bb6c1cb2c122edc689532ea650cc0e1f3fc4ef9fc362aa67d  IJ46030m3a.230623.epkg.Z key_w_csum
        455bf389db97e3df581c4a8de9efe11eab2a579371685b522260a7a898c310cb  IJ47324m5a.230623.epkg.Z key_w_csum
        0672cf52ad47fa275c6507e6ad6b5d335b4cd5a40f566c14344efa2b9edb1535  rpm.rte.4.15.1.1007      key_w_csum
        ae98d2787326d8fca84c80d8dd4859be98d7e37faccad470c1bae0fe28a41a80  rpm.rte.4.15.1.2007      key_w_csum

        These sums should match exactly. The OpenSSL signatures in the tar
        file and on this advisory can also be used to verify the
        integrity of the fixes.  If the sums or signatures cannot be
        confirmed, contact IBM Support at
        http://ibm.com/support/ and describe the discrepancy.         

        openssl dgst -sha256 -verify [pubkey_file] -signature [advisory_file].sig [advisory_file]

        openssl dgst -sha256 -verify [pubkey_file] -signature [ifix_file].sig [ifix_file]

        Published advisory OpenSSL signature file location:

        https://aix.software.ibm.com/aix/efixes/security/zlib_advisory2.asc.sig

    B. FIX AND INTERIM FIX INSTALLATION

        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

Contact IBM Support for questions related to this announcement:

    https://ibm.com/support/

For information on how to securely verify AIX security bulletins and fixes:

    https://www.ibm.com/support/pages/node/6985269

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
https://aix.software.ibm.com/aix/efixes/security/systems_p_os_aix_security_pubkey.txt

To verify the AIX/VIOS security bulletin:

    Published advisory OpenSSL signature file location:

    https://aix.software.ibm.com/aix/efixes/security/zlib_advisory2.asc.sig

    openssl dgst -sha256 -verify [pubkey_file] -signature [advisory_file].sig [advisory_file]

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: AIX is vulnerable to denial of service due to zlib
    (CVE-2022-37434)
    https://www.ibm.com/support/pages/node/7014483

ACKNOWLEDGEMENTS:

None.

CHANGE HISTORY:

First Issued: Tue Jul 25 11:05:17 CDT 2023

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

*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.