IBM SECURITY ADVISORY First Issued: Wed Sep 28 13:38:50 CDT 2022 The most recent version of this document is available here: http://aix.software.ibm.com/aix/efixes/security/zlib_advisory.asc https://aix.software.ibm.com/aix/efixes/security/zlib_advisory.asc ftp://aix.software.ibm.com/aix/efixes/security/zlib_advisory.asc Security Bulletin: AIX is vulnerable to denial of service due to zlib and zlibNX (CVE-2018-25032) =============================================================================== SUMMARY: A vulnerability in zlib and zlibNX could allow a remote attacker to cause a denial of service (CVE-2018-25032). AIX uses zlib and zlibNX as part of its data compression functions. =============================================================================== VULNERABILITY DETAILS: CVEID: CVE-2018-25032 http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2018-25032 https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2018-25032 DESCRIPTION: Zlib is vulnerable to a denial of service, caused by a memory corruption in the deflate operation. By using many distant matches, a remote attacker could exploit this vulnerability to cause the application to crash. CVSS Base Score: 7.5 CVSS Temporal Score: See https://exchange.xforce.ibmcloud.com/vulnerabilities/222615 for the current score CVSS Environmental Score*: Undefined CVSS Vector: (CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H) 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 4.15.1.1005 key_w_fs zlib rpm.rte 4.15.1.2000 4.15.1.2005 key_w_fs zlib For zlibNX: Fileset Lower Level Upper Level KEY PRODUCT(S) --------------------------------------------------------------------- zlibNX.rte 7.2.4.0 7.2.4.7 key_w_fs zlibNX zlibNX.rte 7.3.0.0 7.3.0.1 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 AIX and VIOS fixes can be downloaded via ftp or http from: ftp://aix.software.ibm.com/aix/efixes/security/zlib_fix.tar http://aix.software.ibm.com/aix/efixes/security/zlib_fix.tar https://aix.software.ibm.com/aix/efixes/security/zlib_fix.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) --------------------------------------------------------------- 7.1, 7.2 rpm.rte.4.15.1.1006 key_w_fix zlib 7.3 rpm.rte.4.15.1.2006 key_w_fix zlib VIOS Level Fix KEY PRODUCT(S) --------------------------------------------------------------- 3.1 rpm.rte.4.15.1.1006 key_w_fix zlib For zlibNX: AIX Level Interim Fix (*.Z) KEY PRODUCT(S) ---------------------------------------------------------- 7.2 IJ41754s4a.220829.epkg.Z key_w_fix zlibNX 7.3 IJ42198s2a.220829.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 IJ41754s4a.220829.epkg.Z key_w_fix zlibNX To extract the fixes from the tar file: tar xvf zlib_fix.tar cd zlib_fix 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 ----------------------------------------------------------------------------------------------------- 6e830be2ce0057d12072bef887337b39a5fb97cc6fceafbdf3c9d1c8f6bda8be IJ41754s4a.220829.epkg.Z key_w_csum 91b35e4f334463f49d76e263c70fa8dce09dbc9825d3bb7640b8d186511dfd02 IJ42198s2a.220829.epkg.Z key_w_csum f12ab2fa1cce9129dc27f2d8a6af1f3e5a1075c93da87ff5f67519d19cfd8db1 rpm.rte.4.15.1.1006 key_w_csum 942c99ecb388645676e3f9361b0157406997188f4249ff7d07ee58bf3271cc34 rpm.rte.4.15.1.2006 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: http://aix.software.ibm.com/aix/efixes/security/zlib_advisory.asc.sig https://aix.software.ibm.com/aix/efixes/security/zlib_advisory.asc.sig ftp://aix.software.ibm.com/aix/efixes/security/zlib_advisory.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 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: AIX is vulnerable to denial of service due to zlib and zlibNX (CVE-2018-25032) https://www.ibm.com/support/pages/node/6824891 ACKNOWLEDGEMENTS: None. CHANGE HISTORY: First Issued: Wed Sep 28 13:38:50 CDT 2022 =============================================================================== *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.