CVE-2026-47691 — Netty has Insufficient Bailiwick Validation for NS Records

Affected: netty, Red Hat Cryostat 4 on RHEL 9, Red Hat Build of Apache Camel 3.33 for Quarkus 3.33.2.SP1, Red Hat build of Apache Camel 4.18.1.P1 for Spring Boot 3.5.16, Red Hat build of Quarkus 3.27.4.SP1, Red Hat build of Quarkus 3.33.2.SP1, Red Hat Data Grid 8.6.2, Red Hat JBoss Enterprise Application Platform 7.4 ELS on RHEL 7, Red Hat JBoss Enterprise Application Platform 7.4 ELS on RHEL 8, Red Hat JBoss Enterprise Application Platform 7.4 ELS on RHEL 9 and 21 more

Netty is a network application framework for development of protocol servers and clients. Prior to versions 4.1.135.Final and 4.2.15.Final, Netty's `DnsResolveContext` insufficiently validates the bailiwick of NS records, enabling DNS Cache Poisoning. An attacker controlling an authoritative name server for a subdomain can poison the cache for parent domains (like `.co.uk`). In `io.netty.resolver.dns.DnsResolveContext.AuthoritativeNameServerList#add` method accepts any NS record from the AUTHORITY section as long as the record's name is a suffix of the questionName. Subsequently, the `handleWithAdditional` method caches the associated A records from the ADDITIONAL section directly into the `authoritativeDnsServerCache` under the parent domain's key. This bypasses standard bailiwick rules, where a server authoritative for a subdomain should not be trusted to provide authoritative records for its parent. The poisoned cache is then used for all future resolutions under the parent domain's key. Versions 4.1.135.Final and 4.2.15.Final patch the issue.

GHSA-5pvg-856g-cp85 — Netty has Insufficient Bailiwick Validation for NS Records

Affected: Maven: io.netty:netty-resolver-dns

### Summary Netty's `DnsResolveContext` insufficiently validates the bailiwick of NS records, enabling DNS Cache Poisoning. An attacker controlling an authoritative name server for a subdomain can poison the cache for parent domains (like `.co.uk`).

### Details In `io.netty.resolver.dns.DnsResolveContext.AuthoritativeNameServerList#add` method accepts any NS record from the AUTHORITY section as long as the record's name is a suffix of the questionName.

This means if the resolver queries evil.co.uk., it will accept an NS record claiming authority over co.uk.. Subsequently, the `handleWithAdditional` method caches the associated A records from the ADDITIONAL section directly into the `authoritativeDnsServerCache` under the parent domain's key (co.uk.). This bypasses standard bailiwick rules, where a server authoritative for a subdomain should not be trusted to provide authoritative records for its parent. The poisoned cache is then used for all future resolutions under co.uk..

The `io.netty.resolver.dns.DnsResolveContext.AuthoritativeNameServerList#cache` method only prevents caching if the record is for the root zone (dots == 1).

### Impact DNS Cache Poisoning. Any application using Netty's DNS resolver is impacted.

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CVE-2026-47691 — Netty has Insufficient Bailiwick Validation for NS Records

GHSA-5pvg-856g-cp85 — Netty has Insufficient Bailiwick Validation for NS Records