CVE-2026-47691 is a high-severity security vulnerability in io.netty:netty-resolver-dns (maven), affecting versions >= 4.2.0.Final, <= 4.2.14.Final. It is fixed in 4.2.15.Final, 4.1.135.Final.
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.
CVE-2026-47691 has a CVSS score of 8.7 (High). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment.
A fixed version is available (4.2.15.Final, 4.1.135.Final). Upgrading removes the vulnerable code path.
maven
io.netty:netty-resolver-dns (>= 4.2.0.Final, <= 4.2.14.Final)io.netty:netty-resolver-dns (<= 4.1.134.Final)io.netty:netty-resolver-dns → 4.2.15.Final (maven)io.netty:netty-resolver-dns → 4.1.135.Final (maven)Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter instead of chasing every advisory.
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Upgrade the following packages to resolve this vulnerability:
io.netty:netty-resolver-dns to 4.2.15.Final or laterio.netty:netty-resolver-dns to 4.1.135.Final or laterKodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.
CVE-2026-47691 is a high-severity security vulnerability in io.netty:netty-resolver-dns (maven), affecting versions >= 4.2.0.Final, <= 4.2.14.Final. It is fixed in 4.2.15.Final, 4.1.135.Final.
CVE-2026-47691 has a CVSS score of 8.7 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
io.netty:netty-resolver-dns (maven) versions >= 4.2.0.Final, <= 4.2.14.Final is affected.
Yes. CVE-2026-47691 is fixed in 4.2.15.Final, 4.1.135.Final. Upgrade to this version or later.
Whether CVE-2026-47691 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
io.netty:netty-resolver-dns to 4.2.15.Final or laterio.netty:netty-resolver-dns to 4.1.135.Final or later