IBM SECURITY ADVISORY First Issued: Fri Jan 29 15:43:20 CST 2016 The most recent version of this document is available here: http://aix.software.ibm.com/aix/efixes/security/openssl_advisory16.asc https://aix.software.ibm.com/aix/efixes/security/openssl_advisory16.asc ftp://aix.software.ibm.com/aix/efixes/security/openssl_advisory16.asc Security Bulletin: Vulnerability in MD5 Signature and Hash Algorithm affects OpenSSL on AIX (CVE-2015-7575) =============================================================================== SUMMARY: The MD5 “SLOTH” vulnerability on TLS 1.2 affects OpenSSL on AIX. =============================================================================== VULNERABILITY DETAILS: CVEID: CVE-2015-7575 DESCRIPTION: The TLS protocol could allow weaker than expected security caused by a collision attack when using the MD5 hash function for signing a ServerKeyExchange message during a TLS handshake. An attacker could exploit this vulnerability using man-in-the-middle techniques to impersonate a TLS server and obtain credentials. CVSS Base Score: 7.1 CVSS Temporal Score: See https://exchange.xforce.ibmcloud.com/vulnerabilities/109415 for the current score CVSS Environmental Score*: Undefined CVSS Vector: (CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:L/A:N) AFFECTED PRODUCTS AND VERSIONS: AIX 5.3, 6.1, 7.1, 7.2 VIOS 2.2.x The following fileset levels are vulnerable: key_fileset = osrcaix Fileset Lower Level Upper Level KEY -------------------------------------------------- openssl.base 1.0.1.500 1.0.1.515 key_w_fs 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 openssl.base REMEDIATION: A. FIXES Fixes are available. The fixes can be downloaded via ftp or http from: ftp://aix.software.ibm.com/aix/efixes/security/openssl_fix16.tar http://aix.software.ibm.com/aix/efixes/security/openssl_fix16.tar https://aix.software.ibm.com/aix/efixes/security/openssl_fix16.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. Note that the tar file contains Interim fixes that are based on OpenSSL version. AIX Level Interim Fix (*.Z) Fileset Name(prereq for installation) KEY -------------------------------------------------------------------------------------------- 5.3, 6.1, 7.1, 7.2 101a_fix.160129.epkg.Z openssl.base(1.0.1.515 version) key_w_fix VIOS Level Interim Fix (*.Z) Fileset Name(prereq for installation) KEY -------------------------------------------------------------------------------------------- 2.2.* 101a_fix.160129.epkg.Z openssl.base(1.0.1.515 version) key_w_fix You should verify applying this fix does not cause any compatibility issues. The fix disables MD5 signature hash by default. 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 MD5 signature hash and take appropriate mitigation and remediation actions. To extract the fixes from the tar file: tar xvf openssl_fix16.tar cd openssl_fix16 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 ---------------------------------------------------------------------------------------------------- bfc26950a361720c2a3692e7dd7f5ae13f782f419b634c34fc42add5b4e83724 101a_fix.160129.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 security-alert@austin.ibm.com and describe the discrepancy. openssl dgst -sha1 -verify -signature .sig openssl dgst -sha1 -verify -signature .sig Published advisory OpenSSL signature file location: http://aix.software.ibm.com/aix/efixes/security/openssl_advisory16.asc.sig https://aix.software.ibm.com/aix/efixes/security/openssl_advisory16.asc.sig ftp://aix.software.ibm.com/aix/efixes/security/openssl_advisory16.asc.sig B. 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. 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 Comments regarding the content of this announcement can be directed to: security-alert@austin.ibm.com 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 security-alert@austin.ibm.com 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 v3 Guide: http://www.first.org/cvss/user-guide On-line Calculator v3: http://www.first.org/cvss/calculator/3.0 ACKNOWLEDGEMENTS: Reported to IBM by Karthikeyan Bhargavan at INRIA in Paris, France. CHANGE HISTORY: First Issued: Fri Jan 29 15:43:20 CST 2016 =============================================================================== *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.