CVE-2026-5946

Invalid handling of CLASS != IN

State: Published
Severity: 7.5 High
Published: May 20, 2026
Updated: Sep 17, 2026
Reserved: Apr 9, 2026

Description

Multiple 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.

Scores

CVSS	Score	Vector	Source
3.1	7.5 High	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H	isc
3.1	7.5 High	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H	redhat-SADP

Weaknesses

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

Affected Products

Product	Versions
BIND 9ISC	9.11.0 through 9.16.50Affected 9.18.0 through 9.18.48Affected 9.20.0 through 9.20.22Affected 9.21.0 through 9.21.21Affected 9.11.3-S1 through 9.16.50-S1Affected 9.18.11-S1 through 9.18.48-S1Affected 9.20.9-S1 through 9.20.22-S1Affected

References

CVE-2026-5946vendor-advisory
https://downloads.isc.org/isc/bind9/9.18.49patch
https://downloads.isc.org/isc/bind9/9.20.23patch
https://downloads.isc.org/isc/bind9/9.21.22patch
https://access.redhat.com/security/cve/CVE-2026-5946vdb-entry
RHBZ#2479771issue-tracking
https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-5946.json
https://access.redhat.com/errata/RHSA-2026:60383vendor-advisory
https://access.redhat.com/errata/RHSA-2026:62549vendor-advisory
https://access.redhat.com/errata/RHSA-2026:65851vendor-advisory
https://access.redhat.com/errata/RHSA-2026:24338vendor-advisory
https://access.redhat.com/errata/RHSA-2026:24339vendor-advisory
https://access.redhat.com/errata/RHSA-2026:23360vendor-advisory
https://access.redhat.com/errata/RHSA-2026:57189vendor-advisory
https://access.redhat.com/errata/RHSA-2026:55441vendor-advisory
https://access.redhat.com/errata/RHSA-2026:24367vendor-advisory
https://access.redhat.com/errata/RHSA-2026:24368vendor-advisory
https://access.redhat.com/errata/RHSA-2026:20334vendor-advisory

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