IBM SECURITY ADVISORY First Issued: Mon Nov 2 01:14:47 CST 2026 The most recent version of this document is available here: https://aix.software.ibm.com/aix/efixes/security/bind_advisory32.asc Security Bulletin: Multiple vulnerabilities impact AIX due to ISC BIND =============================================================================== SUMMARY: Vulnerabilities in ISC BIND: DNSSEC Validation / Integrity Bypass : CVE-2026-19033, CVE-2026-19941, CVE-2026-77119 Resolver Crash / Denial of Service : CVE-2026-19662, CVE-2026-19666, CVE-2026-19667, CVE-2026-80274 Resource Exhaustion CPU/Memory : CVE-2026-19668, CVE-2026-75029, CVE-2026-81563, CVE-2026-81736 AIX uses ISC BIND as as part of its DNS functions. =============================================================================== VULNERABILITY DETAILS: CVEID: CVE-2026-19033 https://www.cve.org/CVERecord?id=CVE-2026-19033 DESCRIPTION: For a secondary zone with transfers restricted by TSIG, `named` may start to serve the data provided in a zone transfer before the final message with the TSIG signature arrives. This could allow an attacker that does not actually possess a valid TSIG signature to send unauthorized zone contents to a secondary server. Although no TSIG signature ever arrives, `named` does not rollback to the pre-transfer state. To exploit the vulnerability, the transfer must be a multi-message TCP IXFR, as described by RFC 8945. CVSS Base Score: 6.5 CVSS Vector: (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:L) CVEID: CVE-2026-19662 https://www.cve.org/CVERecord?id=CVE-2026-19662 DESCRIPTION: An attacker may be able to cause a `named` resolver to abort. The attack requires inducing the victim resolver to send multiple queries for a DNSSEC-signed zone hosted by an authoritative server under the control of the attacker. If the auth responds with a particular sequence of crafted answers, and those answers arrive in a particular order with particular timing, the `named` resolver will encounter a use-after-free bug, and abort. CVSS Base Score: 5.9 CVSS Vector: (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H) CVEID: CVE-2026-19666 https://www.cve.org/CVERecord?id=CVE-2026-19666 DESCRIPTION: On a resolver configured to use ``dns64``, if an applicable answer from the authoritative server is malformed in a specific way, the resolver `named` process will exit unexpectedly. 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-2026-19667 https://www.cve.org/CVERecord?id=CVE-2026-19667 DESCRIPTION: If an attacker-controlled authoritative server can produce a negative answer that is exactly 65536 bytes, then a flaw in `named` results in a negative cache entry of 0 bytes. When this entry is subsequently read, `named` aborts. 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-2026-19668 https://www.cve.org/CVERecord?id=CVE-2026-19668 DESCRIPTION: A BIND recursive resolver may experience excessive resource consumption if it encounters large numbers of a particular kind of invalid DNSSEC record. Default limits on "max-records-per-type" and "max-types-per-name" help mitigate the exposure. CVSS Base Score: 5.3 CVSS Vector: (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L) CVEID: CVE-2026-19941 https://www.cve.org/CVERecord?id=CVE-2026-19941 DESCRIPTION: An inapplicable NSEC record may be accepted by a `named` resolver as proof that no wildcard exists, which could allow an attacker at the same or an upstream level of the zone name to mask the existence of a victim's wildcard record. CVSS Base Score: 5.9 CVSS Vector: (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N) CVEID: CVE-2026-75029 https://www.cve.org/CVERecord?id=CVE-2026-75029 DESCRIPTION: In a query response, an attacker may send `named` multiple copies of a record that should only exist once (such as an SOA record). If the RDATA is the same on all the copies, the record is appended to the in-memory RDATA set, which can cause increased memory usage of the negative cache and possibly lead to other memory attack vectors. CVSS Base Score: 5.3 CVSS Vector: (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L) CVEID: CVE-2026-77119 https://www.cve.org/CVERecord?id=CVE-2026-77119 DESCRIPTION: A validly signed NSEC3 from an unrelated sibling zone may be accepted as an insecurity proof, downgrading a secure delegation and letting a forged unsigned answer through. CVSS Base Score: 5.9 CVSS Vector: (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N) CVEID: CVE-2026-80274 https://www.cve.org/CVERecord?id=CVE-2026-80274 DESCRIPTION: If a BIND resolver sends a query for a DNSSEC-signed authoritative zone, and the authoritative server replies with a valid wildcard answer and signed NSEC3 proof, followed by an unsigned NSEC at the same owner name, it will trigger an unexpected program exit. 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-2026-81563 https://www.cve.org/CVERecord?id=CVE-2026-81563 DESCRIPTION: A BIND resolver encountering an SVCB/HTTPS AliasMode record referencing 14 or more SVCB/HTTPS ServiceMode records may fail to properly deallocate internal resources. If this happens repeatedly, resource exhaustion will eventually prevent the resolver from performing new recursive lookups. 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-2026-81736 https://www.cve.org/CVERecord?id=CVE-2026-81736 DESCRIPTION: If a BIND resolver has cached a tree of SVCB/HTTPS AliasMode records, and is then queried for the root of that tree, the resolver will spend disproportionate CPU time constructing the response. 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) AFFECTED PRODUCTS AND VERSIONS: AIX 7.2, 7.3 VIOS 4.1 The vulnerabilities are being addressed for the following filesets: key_fileset = aix Fileset Lower Level Upper Level KEY ---------------------------------------------------------- bind.rte 7.1.916.0 7.1.916.4800 key_w_fs bind.rte 7.2.916.0 7.2.916.4801 key_w_fs bind.rte 7.2.918.0 7.2.918.4900 key_w_fs bind.rte 7.3.916.0 7.3.916.4800 key_w_fs bind.rte 7.3.918.0 7.3.918.4900 key_w_fs bind.rte 7.3.920.2600 7.3.920.2600 key_w_fs Note: A. Latest level of BIND fileset is available 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 bind.rte REMEDIATION: A. FIXES IBM strongly recommends addressing the vulnerability now. The AIX and VIOS fixes can be downloaded via https from: https://aix.software.ibm.com/aix/efixes/security/bind_fix32.tar The fileset update has a dependency on OpenSSL 3.0. OpenSSL 3.0 may be downloaded from: https://www.ibm.com/resources/mrs/assets?source=aixbp The link above is to a tar file containing this signed advisory, install 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. To extract the fixes from the tar file: tar xvf bind_fix32.tar For AIX 7.2 (requires OpenSSL 3.0): tar xvf bind_fix32/72bind920.tar For AIX 7.3 and VIOS 4.1: tar xvf bind_fix32/73bind920.tar IMPORTANT: 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 the fix installation: installp -apYd . bind To install the fix package: installp -aXYd . bind Verify you have retrieved the fixes intact: The checksums below were generated using the "openssl dgst -sha256 [file]" command as the following: openssl dgst -sha256 filename KEY --------------------------------------------------------------------------------------- b9a302c14bcc398d78edae588b7d01ea7837eddbec022da482f9513b4ae457a0 72bind.rte key_w_csum 74b0af640a57f975077fc3f024fb2f5c914e52f1b522e65b1973bdc0fef58a94 73bind.rte key_w_csum openssl dgst -sha512 filename KEY ---------------------------------------------------------------------------------------------------------------------------------------------------------- 963bfa32d8547a0fe83599baea65ca9f6dd5bb14871e5ebaea6e9a0bc1b5b829c2e6129aa11dad670e5884792162e984ca939e2e4b792eb3d52b60545ec3048b 72bind.rte key_4K_w_csum ea56e28ae86f9bb46d8e9f7f66e8a5afa266e176815617625fa671868e3100a020d2f9677ba7246035e494d49424e1613033d122d11c1930d0d6c2350d34a312 73bind.rte 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/bind_advisory32.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": https://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/bind_advisory32.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/7294990 ACKNOWLEDGEMENTS: None. CHANGE HISTORY: Supported fileset level is updated. First Issued: Mon Nov 2 01:14:47 CST 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.