CVE-2026-47691: netty

Vulnerability summary

CVE-2026-47691 is a critical (CVSS 10.0) vulnerability in netty. EPSS estimates a 0.36% chance of exploitation in the next 30 days, higher than 27.9% of scored vulnerabilities.

Timeline

1. 12-06-2026
   PublishedVulnerability first disclosed.
2. 18-09-2026
   Last modifiedVulnerability information updated.

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.

• CWE-345Insufficient Verification of Data AuthenticityThe product does not sufficiently verify the origin or authenticity of data, in a way that causes it to accept invalid data.
• CWE-346Origin Validation ErrorThe product does not properly verify that the source of data or communication is valid.