IBM SECURITY ADVISORY First Issued: Wed Oct 21 05:56:41 CDT 2026 The most recent version of this document is available here: https://aix.software.ibm.com/aix/efixes/security/libxml2_advisory12.asc Security Bulletin: Vulnerabilities in libxml2 (CVE-2026-86140, CVE-2026-86141, CVE-2026-86143, CVE-2026-86144) affect AIX. =============================================================================== SUMMARY: Vulnerabilities in libxml2 could cause stack-based buffer overflow (CVE-2026-86140), A NULL pointer dereference (CVE-2026-86141), An integer overflow (CVE-2026-86143), denial-of-service (CVE-2026-86144). AIX uses libxml2 as part of its XML parsing functions. =============================================================================== VULNERABILITY DETAILS: CVEID: CVE-2026-86140 https://www.cve.org/CVERecord?id=CVE-2026-86140 DESCRIPTION: In libxml2 before 2.15.4, xmlSnprintfElements in valid.c contains a stack-based buffer overflow caused by an unsafe strcat operation. Successful exploitation could result in memory corruption, application crashes, or arbitrary code execution. CVSS Base Score: 7.8 CVSS Vector: (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H) CVEID: CVE-2026-86141 https://www.cve.org/CVERecord?id=CVE-2026-86141 DESCRIPTION: xmlregexp in libxml2 before 2.15.4 contains a NULL pointer dereference in xmlRegNewParserCtxt following a strdup failure. The code fails to properly handle a NULL return value before calculating a string length, potentially causing application crashes. CVSS Base Score: 3.3 CVSS Vector: (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L) CVEID: CVE-2026-86143 https://www.cve.org/CVERecord?id=CVE-2026-86143 DESCRIPTION: In xmlIO in libxml2 before 2.15.4, an inconsistency between xmlOutputWriteCallback and xmlBufUse allows negative length values to reach write callbacks. Missing integer overflow validation may lead to unintended behavior, memory corruption, or application instability. CVSS Base Score: 7.3 CVSS Vector: (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:L) CVEID: CVE-2026-86144 https://www.cve.org/CVERecord?id=CVE-2026-86144 DESCRIPTION: In xinclude in libxml2 before 2.15.4, xmlXIncludeProcess and xmlXIncludeProcessTree fail to propagate parseFlags. This may bypass protections such as XML_PARSE_NONET and could enable XML external entity injection, SSRF, or denial-of-service attacks when external resources are accessed. CVSS Base Score: 7.8 CVSS Vector: (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H) AFFECTED PRODUCTS AND VERSIONS: AIX 7.2, 7.3 VIOS 4.1 The following fileset levels are vulnerable: key_fileset = aix Fileset Lower Level Upper Level KEY --------------------------------------------------------- bos.rte.control 7.2.5.0 7.2.5.208 key_w_fs bos.rte.control 7.3.2.0 7.3.2.4 key_w_fs bos.rte.control 7.3.3.0 7.3.3.3 key_w_fs bos.rte.control 7.3.4.0 7.3.4.2 key_w_fs 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 bos.rte.control REMEDIATION: A. APARS IBM has assigned the following APARs to this problem: AIX Level APAR Availability SP KEY ----------------------------------------------------- 7.2.5 IJ60235 ** SP13 key_w_apar 7.3.2 IJ60688 ** SP5 key_w_apar 7.3.3 IJ60688 ** SP03 key_w_apar 7.3.4 IJ60270 ** SP02 key_w_apar VIOS Level APAR Availability SP KEY ----------------------------------------------------- 4.1.0 IJ60688 ** 4.1.0.50 key_w_apar 4.1.1 IJ60688 ** 4.1.1.30 key_w_apar 4.1.2 IJ60270 ** 4.1.2.20 key_w_apar Subscribe to the APARs here: https://www.ibm.com/support/pages/apar/[apar number] By subscribing, you will receive periodic email alerting you to the status of the APAR, and a link to download the fix once it becomes available. B. FIXES IBM strongly recommends addressing the vulnerability now. AIX and VIOS fixes are available. The fixes are cumulative and address previously issued AIX/VIOS libxml2 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/libxml2_fix12.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. AIX Level Interim Fix (*.Z) KEY ---------------------------------------------- 7.2.5.11 IJ60235sda.261019.epkg.Z key_w_fix 7.2.5.12 IJ60235sda.261019.epkg.Z key_w_fix 7.2.5.13 IJ60235sda.261019.epkg.Z key_w_fix 7.3.2.3 IJ60688s3a.261019.epkg.Z key_w_fix 7.3.2.4 IJ60688s3a.261019.epkg.Z key_w_fix 7.3.2.5 IJ60688s3a.261019.epkg.Z key_w_fix 7.3.3.1 IJ60688s3a.261019.epkg.Z key_w_fix 7.3.3.2 IJ60688s3a.261019.epkg.Z key_w_fix 7.3.3.3 IJ60688s3a.261019.epkg.Z key_w_fix 7.3.4.0 IJ60270s2a.261019.epkg.Z key_w_fix 7.3.4.1 IJ60270s2a.261019.epkg.Z key_w_fix 7.3.4.2 IJ60270s2a.261019.epkg.Z key_w_fix Please note that the above table refers to AIX TL/SP level as opposed to fileset level, i.e., 7.3.2.3 is AIX 7300-02-03. Please reference the Affected Products and Version section above for help with checking installed fileset levels. VIOS Level Interim Fix (*.Z) KEY ----------------------------------------------- 4.1.0.30 IJ60688s3a.261019.epkg.Z key_w_fix 4.1.0.40 IJ60688s3a.261019.epkg.Z key_w_fix 4.1.0.50 IJ60688s3a.261019.epkg.Z key_w_fix 4.1.1.10 IJ60688s3a.261019.epkg.Z key_w_fix 4.1.1.20 IJ60688s3a.261019.epkg.Z key_w_fix 4.1.1.30 IJ60688s3a.261019.epkg.Z key_w_fix 4.1.2.0 IJ60270s2a.261019.epkg.Z key_w_fix 4.1.2.10 IJ60270s2a.261019.epkg.Z key_w_fix 4.1.2.20 IJ60270s2a.261019.epkg.Z key_w_fix To extract the fixes from the tar file: tar xvf libxml2_fix12.tar cd libxml2_fix12 Verify you have retrieved the fixes intact: The checksums below were generated using the following command: "openssl dgst -sha256 [filename]" openssl dgst -sha256 filename KEY ----------------------------------------------------------------------------------------------------- 64c4e2157772d2042e93461b0b84c5910ed76f550b9267fa9a94f654adcf19a0 IJ60235sda.261019.epkg.Z key_w_csum d940b16529352f9f6de67953f27dab0d215fb00d184f58fea5a420f9b679e409 IJ60688s3a.261019.epkg.Z key_w_csum 005a43800ed765f856348e5ab06cbe0188dfeda5caea12e18aa646103ae61bbc IJ60270s2a.261019.epkg.Z key_w_csum The checksums below were generated using the following command: "openssl dgst -sha512 [filename]" openssl dgst -sha512 filename KEY ------------------------------------------------------------------------------------------------------------------------------------------------------------------------ 6f05063b4fcdb15c143e7b2726a59119e9386091951383fba60f5cfa26db53d4f3af3ab55ed3c6f7548c64ab0f15e0b4b073866944fd1b9c714884c30a857619 IJ60235sda.261019.epkg.Z key_4K_w_csum d49b521f067d828f7f825a265938481a2559d71a95bbbc7866c012cba1e5cf0c9af39442b6e53af38aa89dcfa518d91d3548835b574a6706a77e993a1e785dc2 IJ60688s3a.261019.epkg.Z key_4K_w_csum 7a86e018e650d1e2404399c609675711ea149c71cfb25c91971f283520e001fe255e327c2c4042639ff49b08d17614d4b2eeb8071aef0f8c858a94a32aadc0a7 IJ60270s2a.261019.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/libxml2_advisory12.asc.sig C. 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/libxml2_advisory12.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: https://www.ibm.com/support/pages/node/7293277 ACKNOWLEDGEMENTS: None. CHANGE HISTORY: First Issued: Wed Oct 21 05:56:41 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.