IBM SECURITY ADVISORY First Issued: Thu May 28 14:09:50 CDT 2026 The most recent version of this document is available here: https://aix.software.ibm.com/aix/efixes/security/openssh_advisory21.asc Security Bulletin: Multiple vulnerabilities in OpenSSH affect AIX =============================================================================== SUMMARY: There are multiple vulnerabilities in OpenSSH used by AIX (CVE-2026-35385, CVE-2026-35386, CVE-2026-35387, CVE-2026-35388, CVE-2026-35414). OpenSSH is used by AIX for remote login. =============================================================================== VULNERABILITY DETAILS: CVEID: CVE-2026-35385 https://www.cve.org/CVERecord?id=CVE-2026-35385 DESCRIPTION: In OpenSSH before 10.3, a file downloaded by scp may be installed setuid or setgid, an outcome contrary to some users' expectations, if the download is performed as root with -O (legacy scp protocol) and without -p (preserve mode). CVSS Base Score: 8.1 CVSS Vector: (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H) CVEID: CVE-2026-35386 https://www.cve.org/CVERecord?id=CVE-2026-35386 DESCRIPTION: In OpenSSH before 10.3, command execution can occur via shell metacharacters in a username within a command line. This requires a scenario where the username on the command line is untrusted, and also requires a non-default configurations of % in ssh_config. CVSS Base Score: 8.1 CVSS Vector: (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H) CVEID: CVE-2026-35387 https://www.cve.org/CVERecord?id=CVE-2026-35387 DESCRIPTION: OpenSSH before 10.3 can use unintended ECDSA algorithms. Listing of any ECDSA algorithm in PubkeyAcceptedAlgorithms or HostbasedAcceptedAlgorithms is misinterpreted to mean all ECDSA algorithms. CVSS Base Score: 6.5 CVSS Vector: (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:L/A:N) CVEID: CVE-2026-35388 https://www.cve.org/CVERecord?id=CVE-2026-35388 DESCRIPTION: OpenSSH before 10.3 omits connection multiplexing confirmation for proxy-mode multiplexing sessions. CVSS Base Score: 2.5 CVSS Vector: (CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:N/I:L/A:N) CVEID: CVE-2026-35414 https://www.cve.org/CVERecord?id=CVE-2026-35414 DESCRIPTION: OpenSSH before 10.3 mishandles the authorized_keys principals option in uncommon scenarios involving a principals list in conjunction with a Certificate Authority that makes certain use of comma characters. CVSS Base Score: 8.1 CVSS Vector: (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H) AFFECTED PRODUCTS AND VERSIONS: AIX 7.2, 7.3 VIOS 4.1 The vulnerabilities are being addressed in the following filesets: key_fileset = aix Fileset Lower Level Upper Level KEY --------------------------------------------------------------- openssh.base.client 9.2.112.0 9.7.3013.1000 key_w_fs openssh.base.server 9.2.112.0 9.7.3013.1000 key_w_fs openssh.base.client 9.9.3015.1000 9.9.3015.2000 key_w_fs openssh.base.server 9.9.3015.1000 9.9.3015.2000 key_w_fs Note: A. OpenSSH versions below 9.9 are out-of-support. Customers are advised to update to the latest AIX SP or download the latest OpenSSH version from the Web Download site: https://www.ibm.com/resources/mrs/assets?source=aixbp 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 openssh.base.client 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 https from: https://aix.software.ibm.com/aix/efixes/security/openssh_fix21.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 OpenSSH version, and AIX OpenSSH fixes are cumulative. You must be on the 'prereq for installation' level before applying the interim fix. This may require installing a new level(prereq version) first from: https://www.ibm.com/resources/mrs/assets?source=aixbp AIX Level Interim Fix (*.Z) Fileset Name(prereq for installation) KEY --------------------------------------------------------------------------------------- 7.2, 7.3 35414ma.260507.epkg.Z openssh.base(9.9.3015.2000) key_w_fix VIOS Level Interim Fix (*.Z) Fileset Name(prereq for installation) KEY ------------------------------------------------------------------------------------------ 4.1 35414ma.260507.epkg.Z openssh.base(9.9.3015.2000) key_w_fix To extract the fixes from the tar file: tar xvf openssh_fix21.tar cd openssh_fix21 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 ----------------------------------------------------------------------------------------------------- f981975478c82fc5500be4aceb8f3b8925ad89dc1d2d8f7ef8f20beb6ab48fcd 35414ma.260507.epkg.Z key_w_csum openssl dgst -sha512 filename ------------------------------------------------------------------------------------------------------------------------------------------------------------------------ 301eef6d69b5415c0c0576ee4052ac4d5aad11084306a3376d5f317c4a138f4f4884419c09293b1fa15d9e2da5fa2f0a1a1203abb7e27ab9f6caef0c2452d53f 35414ma.260507.epkg.Z key_4K_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/openssh_advisory21.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: https://www.ibm.com/support/pages/managing-interim-fixes-aix 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: 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/openssh_advisory21.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: https://www.first.org/cvss/user-guide On-line Calculator v3: https://www.first.org/cvss/calculator/3.0 RELATED INFORMATION: IBM Secure Engineering Web Portal https://www.ibm.com/support/pages/ibm-security-vulnerability-management IBM Product Security Incident Response Blog https://www.ibm.com/blogs/psirt/ Security Bulletin: https://www.ibm.com/support/pages/node/7274374 ACKNOWLEDGEMENTS: None. CHANGE HISTORY: First Issued: Thu May 28 14:09:50 CDT 2026 =============================================================================== *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.