Security Bulletin
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
DESCRIPTION: A flaw in the libcurl SASL negotiation for LDAP authentication allows an
incomplete handshake sequence to be misinterpreted as a successful
cryptographic verification. An attacker executing a Man-in-the-Middle (MITM)
attack can inject a premature or shortcut response that bypasses complete peer
validation.
CWE: CWE-923: Improper Restriction of Communication Channel to Intended Endpoints
CVSS Source: CISA ADP
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
DESCRIPTION: A flaw in libcurl's handling of HTTP/2 Server Push streams, when the parent
handle is set to share connections with other handles, can lead to
use-after-free in the cleanup process.
CWE: CWE-416: Use After Free
CVSS Source: CISA ADP
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
DESCRIPTION: A flaw in libcurl makes it wrongly reuse an HTTP connection setup for a given
hostname using Negotiate authentication, when the initial request is done
using empty credentials. This can make user B's request get sent over user A's
previously authenticated connection.
CWE: CWE-488: Exposure of Data Element to Wrong Session
CVSS Source: CISA ADP
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
DESCRIPTION: When `CURLOPT_PINNEDPUBLICKEY` is configured alongside 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. Bypassing the
pinning check under these disabled-verification conditions allows
unauthenticated connections to succeed when they should be rejected.
CWE: CWE-295: Improper Certificate Validation
CVSS Source: CISA ADP
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
DESCRIPTION: A flaw in libcurl makes it wrongly reuse an existing HTTPS connection setup
for a given hostname even when using a different Native CA Store setting
(`CURLSSLOPT_NATIVE_CA`) than when the connection was created.
CWE: CWE-488: Exposure of Data Element to Wrong Session
CVSS Source: CISA ADP
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
DESCRIPTION: When libpsl support is enabled, libcurl fails to enforce the Public Suffix
List boundary check when processing a `Set-Cookie` header where the `Domain`
attribute explicitly matches an origin host that is itself a public suffix
(e.g., `Domain=co.uk` set by `co.uk`).
Instead of coercing it into a strict host-only cookie, libcurl saves the
cookie with wildcard domain scope (`.co.uk`). Consequently, the cookie is
inappropriately included in subsequent outbound requests or HTTP redirects to
arbitrary sibling subdomains under the same public suffix (e.g.,
`attacker.co.uk`).
CWE: CWE-201: Insertion of Sensitive Information Into Sent Data
CVSS Source: CISA ADP
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
| Affected Product(s) | Version(s) |
| 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/Fixes
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 following command :
"openssl dgst -sha256 [filename]"
| openssl dgst -sha256 | filename | KEY |
| 5f248dd6f5dfe1472e3cf8f0339268e9d4ba355279c89593759ecd1e5c4cd18a | 18924mc.261006.epkg.Z | key_w_csum |
The checksums below were generated using the following command :
"openssl dgst -sha512 [filename]"
| 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
Get Notified about Future Security Bulletins
References
Acknowledgement
Change History
14 Oct 2026: Initial Publication
*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. In addition to other efforts to address potential vulnerabilities, IBM periodically updates the record of components contained in our product offerings. As part of that effort, if IBM identifies previously unidentified packages in a product/service inventory, we address relevant vulnerabilities regardless of CVE date. Inclusion of an older CVEID does not demonstrate that the referenced product has been used by IBM since that date, nor that IBM was aware of a vulnerability as of that date. We are making clients aware of relevant vulnerabilities as we become aware of them. "Affected Products and Versions" referenced in IBM Security Bulletins are intended to be only products and versions that are supported by IBM and have not passed their end-of-support or warranty date. Thus, failure to reference unsupported or extended-support products and versions in this Security Bulletin does not constitute a determination by IBM that they are unaffected by the vulnerability. Reference to one or more unsupported versions in this Security Bulletin shall not create an obligation for IBM to provide fixes for any unsupported or extended-support products or versions.
Document Location
Worldwide
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Document Information
Modified date:
14 October 2026
Initial Publish date:
14 October 2026
UID
ibm17292372