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CentOS ProjectSENDMAIL_ADVISORY2.ASC

HistoryAug 07, 2015 - 3:15 p.m.

Vulnerability in Diffie-Hellman ciphers affects sendmail on AIX,Vulnerability in Diffie-Hellman ciphers affects sendmail on VIOS

2015-08-0715:15:59

CentOS Project

aix.software.ibm.com

431

4.3 Medium

CVSS2

Attack Vector

NETWORK

Attack Complexity

MEDIUM

Authentication

NONE

Confidentiality Impact

NONE

Integrity Impact

PARTIAL

Availability Impact

NONE

AV:N/AC:M/Au:N/C:N/I:P/A:N

3.7 Low

CVSS3

Attack Vector

NETWORK

Attack Complexity

HIGH

Privileges Required

NONE

User Interaction

NONE

Scope

UNCHANGED

Confidentiality Impact

NONE

Integrity Impact

LOW

Availability Impact

NONE

CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N

0.974 High

EPSS

Percentile

99.9%

JSON

IBM SECURITY ADVISORY

First Issued: Fri Aug 7 15:15:59 CDT 2015
|Updated: Tue Aug 18 09:19:51 CDT 2015
|Update: Added AIX 5.3 vulnerability information

The most recent version of this document is available here:

http://aix.software.ibm.com/aix/efixes/security/sendmail_advisory2.asc
https://aix.software.ibm.com/aix/efixes/security/sendmail_advisory2.asc
ftp://aix.software.ibm.com/aix/efixes/security/sendmail_advisory2.asc

Security Bulletin: Vulnerability in Diffie-Hellman ciphers affects
sendmail on AIX (CVE-2015-4000)

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

SUMMARY:

The Logjam Attack on TLS connections using the Diffie-Hellman (DH) key
exchange protocol affects sendmail when using the sendmail_ssl binary on
AIX.

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

VULNERABILITY DETAILS:

CVEID: CVE-2015-4000
DESCRIPTION: The TLS protocol could allow a remote attacker to obtain
    sensitive information, caused by the failure to properly convey a
    DHE_EXPORT ciphersuite choice. An attacker could exploit this 
    vulnerability using man-in-the-middle techniques to force a downgrade
    to 512-bit export-grade cipher. Successful exploitation could allow
    an attacker to recover the session key as well as modify the contents
    of the traffic. This vulnerability is commonly referred to as
    "Logjam".
CVSS Base Score: 4.3
CVSS Temporal Score: See
    https://exchange.xforce.ibmcloud.com/vulnerabilities/103294 for the
    current score
CVSS Environmental Score*: Undefined
CVSS Vector: (AV:N/AC:M/Au:N/C:P/I:N/A:N)


AFFECTED PRODUCTS AND VERSIONS:

| AIX 5.3, 6.1, 7.1
VIOS 2.2.x

    The following AIX fileset levels are vulnerable:

    AIX Fileset        Lower Level Upper Level KEY
    --------------------------------------------------------

| bos.net.tcp.client 5.3.0.0 5.3.12.10 key_w_fs
bos.net.tcp.client 6.1.0.0 6.1.8.19 key_w_fs
bos.net.tcp.client 6.1.0.0 6.1.9.45 key_w_fs
bos.net.tcp.client 7.1.0.0 7.1.2.19 key_w_fs
bos.net.tcp.client 7.1.0.0 7.1.3.45 key_w_fs

    AIX Fileset (VIOS)  Lower Level           Upper Level
    ------------------------------------------------------------
    bos.net.tcp.client  6.1.0.0(2.2.0.0)      6.1.8.19(2.2.2.6)
    bos.net.tcp.client  6.1.0.0(2.2.0.0)      6.1.9.45(2.2.3.50)


    Note:  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.client

REMEDIATION:

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

        Please note that these only apply to the SSL-enabled
        sendmail binary, /usr/sbin/sendmail_ssl. The default
        sendmail bindary, /usr/sbin/sendmail, is not vulnerable
        to the Logjam attack.

        AIX Level APAR     Availability  SP   KEY
        ---------------------------------------------------
        5.3.12    IV75967  N/A           N/A  key_w_apar
        6.1.8     IV75644  N/A           N/A  key_w_apar 
        6.1.9     IV75643  12/04/15      SP6  key_w_apar
        7.1.2     IV75645  N/A           N/A  key_w_apar 
        7.1.3     IV75646  2/26/16       SP6  key_w_apar

        Subscribe to the APARs here:

        http://www.ibm.com/support/docview.wss?uid=isg1IV75643
        http://www.ibm.com/support/docview.wss?uid=isg1IV75646

        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

        Fixes are available. Please note that the sendmail_ssl fixes
        require a current version of OpenSSL that includes the Logjam
        fix. Please see the previously published OpenSSL bulletin: 

    http://aix.software.ibm.com/aix/efixes/security/openssl_advisory14.asc
    https://aix.software.ibm.com/aix/efixes/security/openssl_advisory14.asc
    ftp://aix.software.ibm.com/aix/efixes/security/openssl_advisory14.asc 


        The sendmail_ssl fixes can be downloaded via ftp or http from:

        ftp://aix.software.ibm.com/aix/efixes/security/sendmail_fix2.tar
        http://aix.software.ibm.com/aix/efixes/security/sendmail_fix2.tar
        https://aix.software.ibm.com/aix/efixes/security/sendmail_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.

        Please note that these only apply to the SSL-enabled
        sendmail binary, /usr/sbin/sendmail_ssl. The default
        sendmail bindary, /usr/sbin/sendmail, is not vulnerable
        to the Logjam attack.

        AIX Level  Interim Fix (*.Z)         KEY
        ------------------------------------------------

| 5.3.12.9 IV75967m9a.150817.epkg.Z key_w_fix
6.1.8.6 IV75644m6a.150731.epkg.Z key_w_fix
6.1.9.5 IV75643m5a.150731.epkg.Z key_w_fix
7.1.2.6 IV75645m6a.150731.epkg.Z key_w_fix
7.1.3.5 IV75646m5a.150731.epkg.Z key_w_fix

        To extract the fixes from the tar file:

        tar xvf sendmail_fix2.tar
        cd sendmail_fix2

        Verify you have retrieved the fixes intact:

        The checksums below were generated using the
        "openssl dgst -sha256 file" command as the followng:

        openssl dgst -sha256                                              filename                 KEY
        -----------------------------------------------------------------------------------------------------

| 9fc6906b826799ee6e98b1da7e4a7f3b41d8db515be46ee043565e6440487015 IV75967m9a.150817.epkg.Z key_w_csum
517637a4871e869ea9322d8c91c94ef8c74ee17821fbdf85f84e52dfd99233f8 IV75644m6a.150731.epkg.Z key_w_csum
af34ca8e20e0440a35dd4fd8caaa051b892f4d30f7cb7fa3f179efcd7f7ab834 IV75643m5a.150731.epkg.Z key_w_csum
e8916a64220b50eb24df48276fb2a8ddbf50e7c42286eee52841aa7e14864c7c IV75645m6a.150731.epkg.Z key_w_csum
ea4f46484d3934fdfdf73293f0ca47abcb38f930e8e5f619fa2af720e390dc4d IV75646m5a.150731.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 AIX Security at
        [email protected] and describe the discrepancy.
        
        openssl dgst -sha1 -verify &lt;pubkey_file&gt; -signature &lt;advisory_file&gt;.sig &lt;advisory_file&gt;

        openssl dgst -sha1 -verify &lt;pubkey_file&gt; -signature &lt;ifix_file&gt;.sig &lt;ifix_file&gt;

        Published advisory OpenSSL signature file location:

        http://aix.software.ibm.com/aix/efixes/security/sendmail_advisory2.asc.sig
        https://aix.software.ibm.com/aix/efixes/security/sendmail_advisory2.asc.sig
        ftp://aix.software.ibm.com/aix/efixes/security/sendmail_advisory2.asc.sig 

    C. FIX AND INTERIM FIX INSTALLATION

        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.

    You should verify applying this configuration change does not cause
    any compatibility issues. If you change the default setting after
    applying the fix, you will expose yourself to the attack described
    above. IBM recommends that you review your entire environment to
    identify other areas where you have enabled the Diffie-Hellman
    key-exchange protocol used in TLS and take appropriate mitigation and
    remediation actions.

WORKAROUNDS AND MITIGATIONS:

    None.

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

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

Comments regarding the content of this announcement can be
directed to:

    [email protected]

To obtain the OpenSSL public key that can be used to verify the
signed advisories and ifixes:

    Download the key from our web page:

http://www.ibm.com/systems/resources/systems_p_os_aix_security_pubkey.txt

To obtain the PGP public key that can be used to communicate
securely with the AIX Security Team via [email protected] you
can either:

    A. Download the key from our web page:

http://www.ibm.com/systems/resources/systems_p_os_aix_security_pgppubkey.txt

    B. Download the key from a PGP Public Key Server. The key ID is:

        0x28BFAA12

Please contact your local IBM AIX support center for any
assistance.

REFERENCES:

Complete CVSS Guide:  http://www.first.org/cvss/cvss-guide.html
On-line Calculator V2:
    http://nvd.nist.gov/cvss.cfm?calculator&adv&version=2

ACKNOWLEDGEMENTS:

CVE-2015-4000 was reported to IBM by The WeakDH team at https://weakdh.org

CHANGE HISTORY:

First Issued: Fri Aug  7 15:15:59 CDT 2015 
Updated: Tue Aug 11 09:47:52 CDT 2015
Update: Changed advisory name to sendmail_advisory2.asc and fix pack to
    sendmail_fix2.tar

| Updated: Tue Aug 18 09:19:51 CDT 2015
| Update: Added AIX 5.3 vulnerability information

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

*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.