CVE-2026-5946

HIGH 7.5

Invalid handling of CLASS != IN

CVSS Score

7.5

EPSS Score

0.0%

EPSS Percentile

0th

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.

CWE	CWE-20 CWE-125 CWE-617 CWE-754 CWE-843
Vendor	isc
Product	bind 9
Published	May 20, 2026
Last Updated	May 20, 2026

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CVSS v3 Breakdown

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

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

High

Affected Versions

ISC / BIND 9

9.11.0 ≤ 9.16.50 9.18.0 ≤ 9.18.48 9.20.0 ≤ 9.20.22 9.21.0 ≤ 9.21.21 9.11.3-S1 ≤ 9.16.50-S1 9.18.11-S1 ≤ 9.18.48-S1 9.20.9-S1 ≤ 9.20.22-S1

References

NVD ↗ CVE.org ↗ EPSS Data ↗

kb.isc.org: https://kb.isc.org/docs/cve-2026-5946 downloads.isc.org: https://downloads.isc.org/isc/bind9/9.18.49 downloads.isc.org: https://downloads.isc.org/isc/bind9/9.20.23 downloads.isc.org: https://downloads.isc.org/isc/bind9/9.21.22

Credits

ISC would like to thank Mcsky23 for bringing this vulnerability to our attention.