Invalid handling of CLASS != IN

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Summary

CVECVE-2026-5946
StatePUBLISHED
Assignerisc
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-05-20 13:16:40 UTC
Updated2026-07-15 01:16:45 UTC
DescriptionMultiple flaws have been identified in `named` related to the handling of DNS messages whose CLASS is not Internet (`IN`) — for example, `CHAOS` or `HESIOD`, or DNS messages that specify meta-classes (`ANY` or `NONE`) in the question section. Specially crafted requests reaching the affected code paths — recursion, dynamic updates (`UPDATE`), zone change notifications (`NOTIFY`), or processing of `IN`-specific record types in non-`IN` data — can cause assertion failures in `named`. This issue affects BIND 9 versions 9.11.0 through 9.16.50, 9.18.0 through 9.18.48, 9.20.0 through 9.20.22, 9.21.0 through 9.21.21, 9.11.3-S1 through 9.16.50-S1, 9.18.11-S1 through 9.18.48-S1, and 9.20.9-S1 through 9.20.22-S1.

Risk And Classification

Primary CVSS: v3.1 7.5 HIGH from ADP

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS: 0.000580000 probability, percentile 0.182180000 (date 2026-05-27)

Problem Types: CWE-20 | CWE-125 | CWE-617 | CWE-754 | CWE-843 | CWE-1287 | CWE-20 CWE-20 Improper Input Validation | CWE-125 CWE-125 Out-of-bounds Read | CWE-617 CWE-617 Reachable Assertion | CWE-754 CWE-754 Improper Check for Unusual or Exceptional Conditions | CWE-843 CWE-843 Access of Resource Using Incompatible Type ('Type Confusion') | CWE-1287 Improper Validation of Specified Type of Input

VersionSourceTypeScoreSeverityVector
3.1ADPCVSS7.5HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
3.1[email protected]Secondary7.5HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
3.10b0ca135-0b70-47e7-9f44-1890c2a1c46cSecondary7.5HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
3.1CNADECLARED7.5HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

NVD Known Affected Configurations (CPE 2.3)

TypeVendorProductVersionUpdateEditionLanguage
Application Isc Bind All All All All
Application Isc Bind All All All All

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA ISC BIND 9 affected 9.11.0 9.16.50 custom Not specified
CNA ISC BIND 9 affected 9.18.0 9.18.48 custom Not specified
CNA ISC BIND 9 affected 9.20.0 9.20.22 custom Not specified
CNA ISC BIND 9 affected 9.21.0 9.21.21 custom Not specified
CNA ISC BIND 9 affected 9.11.3-S1 9.16.50-S1 custom Not specified
CNA ISC BIND 9 affected 9.18.11-S1 9.18.48-S1 custom Not specified
CNA ISC BIND 9 affected 9.20.9-S1 9.20.22-S1 custom Not specified
ADP Red Hat Red Hat Enterprise Linux 10 unaffected 32:9.18.33-15.el10_2.2 * rpm Not specified
ADP Red Hat Red Hat Enterprise Linux 8 unaffected 32:9.16.23-0.22.el8_10.6 * rpm Not specified
ADP Red Hat Red Hat Enterprise Linux 8 unaffected 32:9.11.36-16.el8_10.8 * rpm Not specified
ADP Red Hat Red Hat Enterprise Linux 9 unaffected 32:9.16.23-40.el9_8.2 * rpm Not specified
ADP Red Hat Red Hat Enterprise Linux 9 unaffected 32:9.18.29-14.el9_8.2 * rpm Not specified
ADP Red Hat Red Hat Hardened Images unaffected 9.18.49-1.hum1 * rpm Not specified
ADP Red Hat Red Hat Enterprise Linux 6 Not specified Not specified
ADP Red Hat Red Hat Enterprise Linux 7 Not specified Not specified
ADP Red Hat Red Hat Enterprise Linux 9 Not specified Not specified
ADP Red Hat Red Hat OpenShift Container Platform 4 Not specified Not specified

References

ReferenceSourceLinkTags
downloads.isc.org/isc/bind9/9.21.22 [email protected] downloads.isc.org Patch
access.redhat.com/errata/RHSA-2026:23360 0b0ca135-0b70-47e7-9f44-1890c2a1c46c access.redhat.com
access.redhat.com/errata/RHSA-2026:24367 0b0ca135-0b70-47e7-9f44-1890c2a1c46c access.redhat.com
access.redhat.com/errata/RHSA-2026:24368 0b0ca135-0b70-47e7-9f44-1890c2a1c46c access.redhat.com
security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-5946.json 0b0ca135-0b70-47e7-9f44-1890c2a1c46c security.access.redhat.com
access.redhat.com/errata/RHSA-2026:24339 0b0ca135-0b70-47e7-9f44-1890c2a1c46c access.redhat.com
downloads.isc.org/isc/bind9/9.20.23 [email protected] downloads.isc.org Patch
bugzilla.redhat.com/show_bug.cgi 0b0ca135-0b70-47e7-9f44-1890c2a1c46c bugzilla.redhat.com
access.redhat.com/security/cve/CVE-2026-5946 0b0ca135-0b70-47e7-9f44-1890c2a1c46c access.redhat.com
access.redhat.com/errata/RHSA-2026:24338 0b0ca135-0b70-47e7-9f44-1890c2a1c46c access.redhat.com
access.redhat.com/errata/RHSA-2026:20334 0b0ca135-0b70-47e7-9f44-1890c2a1c46c access.redhat.com
downloads.isc.org/isc/bind9/9.18.49 [email protected] downloads.isc.org Patch
kb.isc.org/docs/cve-2026-5946 [email protected] kb.isc.org Vendor Advisory
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Vendor Comments And Credit

Discovery Credit

CNA: ISC would like to thank Mcsky23 for bringing this vulnerability to our attention. (en)

Additional Advisory Data

SourceTimeEvent
ADP2026-05-19T09:57:49.705ZReported to Red Hat.
ADP2026-05-21T12:32:55.602ZMade public.

Solutions

CNA: Upgrade to the patched release most closely related to your current version of BIND 9: 9.18.49, 9.20.23, 9.21.22, 9.18.49-S1, or 9.20.23-S1.

ADP: RHSA-2026:24338: Red Hat Enterprise Linux AppStream (v. 10), Red Hat Enterprise Linux CodeReady Linux Builder (v. 10)

ADP: RHSA-2026:24339: Red Hat Enterprise Linux AppStream (v. 8), Red Hat Enterprise Linux BaseOS (v. 8)

ADP: RHSA-2026:23360: Red Hat Enterprise Linux AppStream (v. 8), Red Hat Enterprise Linux CRB (v. 8)

ADP: RHSA-2026:24367: Red Hat Enterprise Linux AppStream (v. 9), Red Hat Enterprise Linux CodeReady Linux Builder (v. 9)

ADP: RHSA-2026:24368: Red Hat Enterprise Linux AppStream (v. 9), Red Hat Enterprise Linux CodeReady Linux Builder (v. 9)

ADP: RHSA-2026:20334: Red Hat Hardened Images

Workarounds

CNA: Don't configure zones other than Internet (`IN`) class. Furthermore, do not expose the server that allows DNS Dynamic Update to the general Internet.

ADP: Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.

Exploits

CNA: We are not aware of any active exploits.

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