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Vulnerability · Published Jun 12, 2026 · Assigned by GitHub_M

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

High 8.7

In plain English

A high-severity insufficient verification of data authenticity in netty from netty. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 31% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)8.7High
Exploit odds (30 days)0.4%top 68.7% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

Official description

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 packages & fixed versions

EcosystemPackageFixed inAdvisory
Debian:12nettyno fix listedDEBIAN-CVE-2026-47691
Debian:13nettyno fix listedDEBIAN-CVE-2026-47691
Debian:14nettyno fix listedDEBIAN-CVE-2026-47691
Mavenio.netty:netty-resolver-dns4.1.135.FinalGHSA-5pvg-856g-cp85
Mavenio.netty:netty-resolver-dns4.2.15.FinalGHSA-5pvg-856g-cp85
Ubuntu:25.10nettyno fix listedUBUNTU-CVE-2026-47691
Ubuntu:26.10nettyno fix listedUBUNTU-CVE-2026-47691

Affected products (as reported)

VendorProductVersions
netty netty >= 4.2.0.Final, < 4.2.15.Final< 4.1.135.Final

Weakness: CWE-345, CWE-346 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:N

References