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

Description (CNA)

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.

Affected (CNA)

Vendor / product	Versions
netty / netty	affected >= 4.2.0.Final, < 4.2.15.Final; affected < 4.1.135.Final

CWE

CWE-345

References

ADP enrichment

CISA-ADP

No English description supplied.

No references supplied.

redhat-SADP

A flaw was found in Netty's `DnsResolveContext`. An attacker controlling an authoritative name server for a subdomain can exploit this vulnerability by providing crafted NS records that are insufficiently validated. This allows the attacker to poison the DNS cache for parent domains, bypassing standard bailiwick rules. Consequently, future DNS resolutions for the affected parent domain will use the poisoned cache, potentially redirecting users to malicious servers and leading to information disclosure or integrity compromise.