IBM SECURITY ADVISORY First Issued: Thu Feb 24 14:37:23 CST 2022 The most recent version of this document is available here: http://aix.software.ibm.com/aix/efixes/security/smbcd_advisory.asc https://aix.software.ibm.com/aix/efixes/security/smbcd_advisory.asc ftp://aix.software.ibm.com/aix/efixes/security/smbcd_advisory.asc Security Bulletin: Vulnerability in the AIX smbcd daemon (CVE-2021-38993) =============================================================================== SUMMARY: There is a vulnerability in the AIX smbcd daemon. =============================================================================== VULNERABILITY DETAILS: CVEID: CVE-2021-38993 http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-38993 https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-38993 DESCRIPTION: IBM AIX could allow a non-privileged local user to exploit a vulnerability in the smbcd daemon to cause a denial of service. CVSS Base Score: 6.2 CVSS Temporal Score: See https://exchange.xforce.ibmcloud.com/vulnerabilities/212962 for the current score CVSS Environmental Score*: Undefined CVSS Vector: (CVSS:3.0/AV:L/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 = osrcaix Fileset Lower Level Upper Level KEY ------------------------------------------------------------- smbc.rte 7.1.0.0 7.1.302.6 key_w_fs smbc.rte 7.2.0.0 7.2.302.6 key_w_fs To determine if your system is vulnerable, execute the following commands: lslpp -L | grep -i smbc.rte REMEDIATION: FIXES The fixes can be downloaded via ftp or http from: ftp://aix.software.ibm.com/aix/efixes/security/smbcd_fix.tar http://aix.software.ibm.com/aix/efixes/security/smbcd_fix.tar https://aix.software.ibm.com/aix/efixes/security/smbcd_fix.tar The latest SMB client fileset may also be downloaded from: https://www.ibm.com/resources/mrs/assets?source=aixbp To extract the fixes from the tar file: For AIX 7.1: tar xvf smbcd_fix.tar gunzip smbc_302_fileset_71.tar.gz | tar xvf For AIX 7.2, 7.3, and VIOS 3.1: tar xvf smbcd_fix.tar gunzip smbc_302_fileset_72.tar.gz | tar xvf 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 the fix installation: installp -apYd . smbc To install the fix package: installp -aXYd . smbc Verify you have retrieved the fixes intact: The checksums below were generated using the "openssl dgst -sha256 [file]" command as the following: openssl dgst -sha256 filename KEY ------------------------------------------------------------------------------------------------------- 82386d9913a386c234dcef6bafa53c803d173760218cea34b94645ab18a89f1f smbc_302_fileset_71.tar.gz key_w_csum ee3966422b87e95b3cdba9537f6276c8e48be9d89ca409fbd258c2a20230034b smbc_302_fileset_72.tar.gz 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 Support at https://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 [fix_file].sig [fix_file] Published advisory OpenSSL signature file location: http://aix.software.ibm.com/aix/efixes/security/smbcd_advisory.asc.sig https://aix.software.ibm.com/aix/efixes/security/smbcd_advisory.asc.sig ftp://aix.software.ibm.com/aix/efixes/security/smbcd_advisory.asc.sig 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 https://www.ibm.com/support/mynotifications To view previously issued advisories, please visit: http://www14.software.ibm.com/webapp/set2/subscriptions/onvdq https://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 https://www.first.org/cvss/user-guide On-line Calculator v3: http://www.first.org/cvss/calculator/3.0 https://www.first.org/cvss/calculator/3.0 RELATED INFORMATION: Security Bulletin: Vulnerabilities in the AIX smbcd daemon (CVE-2021-38993) https://www.ibm.com/support/pages/node/6559320 ACKNOWLEDGEMENTS: None. CHANGE HISTORY: First Issued: Thu Feb 24 14:37:23 CST 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.