AIX is vulnerable to email spoofing due to sendmail (CVE-2023-51765)

IBM SECURITY ADVISORY

First Issued: Thu Apr 11 15:33:45 CDT 2024

The most recent version of this document is available here:
https://aix.software.ibm.com/aix/efixes/security/sendmail_advisory4.asc

Security Bulletin: AIX is vulnerable to email spoofing due to sendmail
(CVE-2023-51765)

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

SUMMARY:

Vulnerability in sendmail could allow a remote attacker to spoof an
email (CVE-2023-51765).

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

VULNERABILITY DETAILS:

CVEID: CVE-2023-51765
    https://vulners.com/cve/CVE-2023-51765
DESCRIPTION: Proofpoint sendmail is vulnerable to SMTP smuggling, caused
    by improper handling of line endings . in an email message. By
    sending a specially crafted request using SMTP MAIL/RCPT/DATA
    commands, an attacker could exploit this vulnerability to spoof an
    email message from any MAIL FROM address.
CVSS Base Score: 6.5
CVSS Temporal Score: See 
    https://exchange.xforce.ibmcloud.com/vulnerabilities/275914
    for the current score
CVSS Environmental Score*: Undefined
CVSS Vector: (CVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N)


AFFECTED PRODUCTS AND VERSIONS:

    AIX 7.2, 7.3
    VIOS 3.1, 4.1

    The vulnerabilities in the following filesets are being addressed:
    
    key_fileset = aix

    Fileset                 Lower Level  Upper Level KEY 
    ---------------------------------------------------------
    bos.net.tcp.sendmail    7.2.5.0      7.2.5.101   key_w_fs
    bos.net.tcp.sendmail    7.2.5.200    7.2.5.200   key_w_fs
    bos.net.tcp.sendmail    7.3.0.0      7.3.0.0     key_w_fs
    bos.net.tcp.sendmail    7.3.1.0      7.3.1.0     key_w_fs
    bos.net.tcp.sendmail    7.3.2.0      7.3.2.0     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 bos.net.tcp.sendmail


REMEDIATION:

    A. APARS
        
        IBM has assigned the following APARs to this problem:


        AIX Level APAR     Availability  SP        KEY
        ---------------------------------------------------------
        7.2.5     IJ50424  **            SP08      key_w_apar
        7.3.0     IJ50433  **            N/A       key_w_apar
        7.3.1     IJ50432  **            SP04      key_w_apar
        7.3.2     IJ50428  **            SP02      key_w_apar

        VIOS Level APAR    Availability  SP        KEY
        ---------------------------------------------------------
        3.1.3      IJ50508 **            N/A       key_w_apar
        3.1.4      IJ50424 **            3.1.4.40  key_w_apar
        4.1.0      IJ50428 **            4.1.0.20  key_w_apar


        Subscribe to the APARs here:

        https://www.ibm.com/support/pages/apar/[APAR Number]

        By subscribing, you will receive periodic email alerting you
        to the status of the APAR, and a link to download the fix once
        it becomes available.

    B. FIXES

        IBM strongly recommends addressing the vulnerability now.

        AIX and VIOS fixes are available.

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

        https://aix.software.ibm.com/aix/efixes/security/sendmail_fix4.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.


        AIX Level  Interim Fix (*.Z)         KEY
        ----------------------------------------------
        7.2.5.5    IJ50424s7a.240315.epkg.Z  key_w_fix
        7.2.5.6    IJ50424s7a.240315.epkg.Z  key_w_fix
        7.2.5.7    IJ50424s7a.240315.epkg.Z  key_w_fix
        7.3.0.2    IJ50433s4a.240315.epkg.Z  key_w_fix
        7.3.0.3    IJ50433s4a.240315.epkg.Z  key_w_fix
        7.3.0.4    IJ50433s4a.240315.epkg.Z  key_w_fix
        7.3.1.1    IJ50432s3a.240315.epkg.Z  key_w_fix
        7.3.1.2    IJ50432s3a.240315.epkg.Z  key_w_fix
        7.3.1.3    IJ50432s3a.240315.epkg.Z  key_w_fix
        7.3.2.1    IJ50428s1a.240315.epkg.Z  key_w_fix

        Please note that the above table refers to AIX TL/SP level as
        opposed to fileset level, i.e., 7.2.5.6 is AIX 7200-05-06.

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

        VIOS Level  Interim Fix (*.Z)         KEY
        -----------------------------------------------
        3.1.3.21    IJ50508s1a.240325.epkg.Z  key_w_fix
        3.1.3.30    IJ50508s1a.240325.epkg.Z  key_w_fix
        3.1.3.40    IJ50508s1a.240325.epkg.Z  key_w_fix
        3.1.4.10    IJ50424s7a.240315.epkg.Z  key_w_fix
        3.1.4.21    IJ50424s7a.240315.epkg.Z  key_w_fix
        3.1.4.31    IJ50424s7a.240315.epkg.Z  key_w_fix
        4.1.0.10    IJ50428s1a.240315.epkg.Z  key_w_fix


        To extract the fixes from the tar file:

        tar xvf sendmail_fix4.tar
        cd sendmail_fix4

        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
        -----------------------------------------------------------------------------------------------------
        951415e087dbfd68eb9ea91ccd8c0abc4489327353ec1c7bf2b79cf2652b2071  IJ50424s7a.240315.epkg.Z key_w_csum
        e6f8c5e65efb44e511ad994beef66ab0ec21c688bce2ec301c44f86eedefdbaf  IJ50428s1a.240315.epkg.Z key_w_csum
        0a92f21c0674787b55a30877ba340dc9f3f8cae7f40fb0c027178094b87a5bc8  IJ50432s3a.240315.epkg.Z key_w_csum
        cc5138e829b8fa8403bb98365a2b1fb42f243b561cb5dc8a8f8e20448d982816  IJ50433s4a.240315.epkg.Z key_w_csum
        a11763ab61f97ea0dc44954d4974df4e84047c8cb49a88acde5492de29eb07eb  IJ50508s1a.240325.epkg.Z 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/sendmail_advisory4.asc.sig

    C. 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:

        https://www.ibm.com/support/pages/managing-interim-fixes-aix

        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:

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/sendmail_advisory4.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 email spoofing due to sendmail
    (CVE-2023-51765)
    https://www.ibm.com/support/pages/node/7148150

ACKNOWLEDGEMENTS:

None.

CHANGE HISTORY:

First Issued: Thu Apr 11 15:33:45 CDT 2024

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

*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.