IBM SECURITY ADVISORY First Issued: Fri Jun 26 01:16:13 CDT 2026 The most recent version of this document is available here: https://aix.software.ibm.com/aix/efixes/security/curl_advisory10.asc Security Bulletin: Multiple vulnerabilities impacts AIX due to cURL libcurl (CVE-2025-14819, CVE-2026-1965, CVE-2026-3783, CVE-2026-3784, CVE-2026-5545) =============================================================================== SUMMARY: Multiple vulnerabilities in the curl/libcurl are related to TLS certificate validation logic and unauthorized actions. =============================================================================== VULNERABILITY DETAILS: CVEID: CVE-2025-14819 https://www.cve.org/CVERecord?id=CVE-2025-14819 DESCRIPTION: When doing TLS related transfers with reused easy or multi handles and altering the `CURLSSLOPT_NO_PARTIALCHAIN` option, libcurl could accidentally reuse a CA store cached in memory for which the partial chain option was reversed. Contrary to the user's wishes and expectations. This could make libcurl find and accept a trust chain that it otherwise would not. CVSS Base score: 5.3 CVSS Environmental Score*: Undefined CVSS Vector: (CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:N/A:N) CVEID: CVE-2026-1965 https://www.cve.org/CVERecord?id=CVE-2026-1965 DESCRIPTION: libcurl can in some circumstances reuse the wrong connection when asked to do an Negotiate-authenticated HTTP or HTTPS request. libcurl features a pool of recent connections so that subsequent requests can reuse an existing connection to avoid overhead. When reusing a connection a range of criterion must first be met. Due to a logical error in the code, a request that was issued by an application could wrongfully reuse an existing connection to the same server that was authenticated using different credentials. One underlying reason being that Negotiate sometimes authenticates *connections* and not *requests*, contrary to how HTTP is designed to work. An application that allows Negotiate authentication to a server (that responds wanting Negotiate) with `user1:password1` and then does another operation to the same server also using Negotiate but with `user2:password2` (while the previous connection is still alive) - the second request wrongly reused the same connection and since it then sees that the Negotiate negotiation is already made, it just sends the request over that connection thinking it uses the user2 credentials when it is in fact still using the connection authenticated for user1... The set of authentication methods to use is set with `CURLOPT_HTTPAUTH`. Applications can disable libcurl's reuse of connections and thus mitigate this problem, by using one of the following libcurl options to alter how connections are or are not reused: `CURLOPT_FRESH_CONNECT`, `CURLOPT_MAXCONNECTS` and `CURLMOPT_MAX_HOST_CONNECTIONS` (if using the curl_multi API). CVSS Base score: 6.5 CVSS Environmental Score*: Undefined CVSS Vector: (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N) CVEID: CVE-2026-3783 https://www.cve.org/CVERecord?id=CVE-2026-3783 DESCRIPTION: When an OAuth2 bearer token is used for an HTTP(S) transfer, and that transfer performs a redirect to a second URL, curl could leak that token to the second hostname under some circumstances. If the hostname that the first request is redirected to has information in the used .netrc file, with either of the `machine` or `default` keywords, curl would pass on the bearer token set for the first host also to the second one. CVSS Base score: 5.3 CVSS Environmental Score*: Undefined CVSS Vector: (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N) CVEID: CVE-2026-3784 https://www.cve.org/CVERecord?id=CVE-2026-3784 DESCRIPTION: curl would wrongly reuse an existing HTTP proxy connection doing CONNECT to a server, even if the new request uses different credentials for the HTTP proxy. The proper behavior is to create or use a separate connection. CVSS Base score: 6.5 CVSS Environmental Score*: Undefined CVSS Vector: (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N) CVEID: CVE-2026-5545 https://www.cve.org/CVERecord?id=CVE-2026-5545 DESCRIPTION: libcurl might in some circumstances reuse the wrong connection when asked to do an authenticated HTTP(S) request after a Negotiate-authenticated one, when both use the same host. libcurl features a pool of recent connections so that subsequent requests can reuse an existing connection to avoid overhead. When reusing a connection a range of criteria must be met. Due to a logical error in the code, a request that was issued by an application could wrongfully reuse an existing connection to the same server that was authenticated using different credentials. An application that first uses Negotiate authentication to a server with `user1:password1` and then does another operation to the same server asking for any authentication method but for `user2:password2` (while the previous connection is still alive) - the second request gets confused and wrongly reuses the same connection and sends the new request over that connection thinking it uses a mix of user1's and user2's credentials when it is in fact still using the connection authenticated for user1... CVSS Base score: 6.5 CVSS Environmental Score*: Undefined CVSS Vector: (CVSS:3.1/AV:N/AC:H/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_fix10.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 3784ma.260518.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_fix10.tar cd curl_fix10 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 ----------------------------------------------------------------------------------------------------- 1554c73f9f181291b515225a96c2f241488d513a73fa1419182fb5b33b4a6c47 3784ma.260518.epkg.Z key_w_csum The checksums below were generated using the "openssl dgst -sha512 [filename]" command as the following: openssl dgst -sha512 filename ------------------------------------------------------------------------------------------------------------------------------------------------------------------------ 817030720de4e128685e6f4dde802d6b448499d61505216765797d5fec38cdce93d288fed1a9a7942586d5e72bf296f748862659cb19329b71d917718dd58cb2 3784ma.260518.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/curl_advisory10.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_advisory10.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/ ACKNOWLEDGEMENTS: None. CHANGE HISTORY: First Issued: Fri Jun 26 01:16:13 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.