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://cve.mitre.org/cgi-bin/cvename.cgi?name=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.