Invalid handling of CLASS != IN
Summary
| CVE | CVE-2026-5946 |
|---|---|
| State | PUBLISHED |
| Assigner | isc |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-05-20 13:16:40 UTC |
| Updated | 2026-05-21 15:24:29 UTC |
| 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. |
Risk And Classification
Primary CVSS: v3.1 7.5 HIGH from [email protected]
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-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')
| Version | Source | Type | Score | Severity | Vector |
|---|---|---|---|---|---|
| 3.1 | [email protected] | Primary | 7.5 | HIGH | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |
| 3.1 | CNA | DECLARED | 7.5 | HIGH | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |
CVSS v3.1 Breakdown
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)
Vendor Declared Affected Products
| Source | Vendor | Product | Version | Platforms |
|---|---|---|---|---|
| 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 |
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| downloads.isc.org/isc/bind9/9.21.22 | [email protected] | downloads.isc.org | Patch |
| downloads.isc.org/isc/bind9/9.20.23 | [email protected] | downloads.isc.org | Patch |
| 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
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.
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.
Exploits
CNA: We are not aware of any active exploits.