IBM SECURITY ADVISORY First Issued: Wed Oct 14 00:51:44 CDT 2026 The most recent version of this document is available here: https://aix.software.ibm.com/aix/efixes/security/curl_advisory13.asc Security Bulletin: Multiple vulnerabilities impacts AIX due to cURL libcurl. =============================================================================== SUMMARY: Multiple vulnerabilities in the curl/libcurl are related to input validation flaws (CVE-2026-13608), memory corruption (CVE-2026-18924), information disclosure (CVE-2026-19931), denial of service (CVE-2026-80230), privilege escalation (CVE-2026-80231), and security policy bypass (CVE-2026-82209). =============================================================================== VULNERABILITY DETAILS: CVEID: CVE-2026-13608 https://www.cve.org/CVERecord?id=CVE-2026-13608 DESCRIPTION: A flaw in libcurl SASL negotiation for LDAP authentication allows an incomplete handshake sequence to be misinterpreted as a successful cryptographic verification. An attacker performing a Man-in-the-Middle (MITM) attack can inject a premature or shortcut response that bypasses complete peer validation. CVSS Base Score: 7.4 CVSS Vector: (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N) CVEID: CVE-2026-18924 https://www.cve.org/CVERecord?id=CVE-2026-18924 DESCRIPTION: A flaw in libcurl's handling of HTTP/2 Server Push streams, when the parent handle is configured to share connections with other handles, can lead to a use-after-free condition during the cleanup process. CVSS Base Score: 9.1 CVSS Vector: (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H) CVEID: CVE-2026-19931 https://www.cve.org/CVERecord?id=CVE-2026-19931 DESCRIPTION: A flaw in libcurl causes reuse of an HTTP connection established for a hostname using Negotiate authentication when the initial request used empty credentials. This may result in user B's request being sent over user A's previously authenticated connection. CVSS Base Score: 9.8 CVSS Vector: (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H) CVEID: CVE-2026-80230 https://www.cve.org/CVERecord?id=CVE-2026-80230 DESCRIPTION: When CURLOPT_PINNEDPUBLICKEY is configured together with options that disable standard peer verification (CURLOPT_SSL_VERIFYPEER=0 and CURLOPT_SSL_VERIFYHOST=0), libcurl fails to enforce public key pinning on connections established without a presented server certificate. This allows unauthenticated connections to succeed when they should be rejected. CVSS Base Score: 7.5 CVSS Vector: (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H) CVEID: CVE-2026-80231 https://www.cve.org/CVERecord?id=CVE-2026-80231 DESCRIPTION: A flaw in libcurl causes reuse of an existing HTTPS connection for a hostname even when a different Native CA Store setting (CURLSSLOPT_NATIVE_CA) is used than the one applied when the connection was originally created. CVSS Base Score: 7.5 CVSS Vector: (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H) CVEID: CVE-2026-82209 https://www.cve.org/CVERecord?id=CVE-2026-82209 DESCRIPTION: When libpsl support is enabled, libcurl fails to enforce the Public Suffix List boundary check for Set-Cookie headers whose Domain attribute explicitly matches an origin host that is itself a public suffix. As a result, cookies may be stored with wildcard domain scope and sent to arbitrary sibling subdomains under the same public suffix. CVSS Base Score: 8.2 CVSS Vector: (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:N) AFFECTED PRODUCTS AND VERSIONS: AIX 7.3 The following fileset levels are vulnerable: key_fileset = aix Fileset Lower Level Upper Level KEY --------------------------------------------------------- oss.lib.libcurl 7.79.1.0 7.79.1.0 key_w_fs oss.lib.libcurl 8.1.2.0 8.1.2.0 key_w_fs oss.lib.libcurl 8.5.0.0 8.5.0.2 key_w_fs Note: This bulletin does not apply to versions of curl installed from the AIX Toolbox. 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 oss.lib.libcurl REMEDIATION: A. FIXES IBM strongly recommends addressing the vulnerability now. AIX fixes are available. The AIX fixes can be downloaded via https from: https://aix.software.ibm.com/aix/efixes/security/curl_fix13.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 Curl version, and AIX Curl fixes are cumulative. AIX Level Interim Fix (*.Z) KEY -------------------------------------------------- 7.3 18924mc.261006.epkg.Z key_w_fix Please reference the Affected Products and Version section above for help with checking installed fileset levels. To extract the fixes from the tar file: tar xvf curl_fix13.tar cd curl_fix13 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 ----------------------------------------------------------------------------------------------------- 5f248dd6f5dfe1472e3cf8f0339268e9d4ba355279c89593759ecd1e5c4cd18a 18924mc.261006.epkg.Z key_w_csum The checksums below were generated using the "openssl dgst -sha512 [filename]" command as the following: openssl dgst -sha512 filename KEY ------------------------------------------------------------------------------------------------------------------------------------------------------------------------ aeef4aa2ea8ee841920491de15285eddc6a9af57116f875145277236eeafc99fb6d0318813045aac608bd2023bf00ed6cd896884feaf82d81043de05674d9136 18924mc.261006.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 integrityi 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/curl_advisory13.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/curl_advisory13.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/7292372 ACKNOWLEDGEMENTS: None. CHANGE HISTORY: First Issued: Wed Oct 14 00:51:44 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.