{"id":"CVE-2026-47691","aliases":["GHSA-5pvg-856g-cp85"],"url":"https://o3.security/vulnerability/CVE-2026-47691","summary":"Netty has Insufficient Bailiwick Validation for NS Records","details":"### Summary\nNetty'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`).\n\n### Details\nIn `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.\n\nThis 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..\n\nThe `io.netty.resolver.dns.DnsResolveContext.AuthoritativeNameServerList#cache` method only prevents caching if the record is for the root zone (dots == 1).\n\n### Impact\nDNS Cache Poisoning. Any application using Netty's DNS resolver is impacted.","published":"2026-06-12T14:33:16.595Z","modified":"2026-09-20T11:46:04.741662531Z","cvss":{"score":8.7,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:N"},"epss":{"score":0.00318,"percentile":0.24762,"asOf":"2026-09-17"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"Maven","name":"io.netty:netty-resolver-dns","fixedVersion":"4.2.15.Final"},{"ecosystem":"Maven","name":"io.netty:netty-resolver-dns","fixedVersion":"4.1.135.Final"}],"fix":null,"references":[{"type":"WEB","url":"https://github.com/netty/netty/releases/tag/netty-4.1.135.Final"},{"type":"WEB","url":"https://github.com/netty/netty/releases/tag/netty-4.2.15.Final"},{"type":"WEB","url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-47691.json"},{"type":"ADVISORY","url":"https://access.redhat.com/errata/RHSA-2026:26017"},{"type":"ADVISORY","url":"https://access.redhat.com/errata/RHSA-2026:26018"},{"type":"ADVISORY","url":"https://access.redhat.com/errata/RHSA-2026:26586"},{"type":"ADVISORY","url":"https://access.redhat.com/errata/RHSA-2026:34608"},{"type":"ADVISORY","url":"https://access.redhat.com/errata/RHSA-2026:37390"},{"type":"ADVISORY","url":"https://access.redhat.com/errata/RHSA-2026:41951"},{"type":"ADVISORY","url":"https://access.redhat.com/errata/RHSA-2026:48151"},{"type":"ADVISORY","url":"https://access.redhat.com/errata/RHSA-2026:49700"},{"type":"ADVISORY","url":"https://access.redhat.com/errata/RHSA-2026:49701"},{"type":"ADVISORY","url":"https://access.redhat.com/errata/RHSA-2026:50085"},{"type":"ADVISORY","url":"https://access.redhat.com/errata/RHSA-2026:53644"},{"type":"ADVISORY","url":"https://access.redhat.com/errata/RHSA-2026:53645"},{"type":"ADVISORY","url":"https://access.redhat.com/errata/RHSA-2026:53646"},{"type":"ADVISORY","url":"https://access.redhat.com/errata/RHSA-2026:54435"},{"type":"ADVISORY","url":"https://access.redhat.com/errata/RHSA-2026:62260"},{"type":"ADVISORY","url":"https://access.redhat.com/errata/RHSA-2026:65126"},{"type":"ADVISORY","url":"https://access.redhat.com/security/cve/CVE-2026-47691"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/47xxx/CVE-2026-47691.json"},{"type":"ADVISORY","url":"https://github.com/netty/netty/security/advisories/GHSA-5pvg-856g-cp85"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-47691"},{"type":"REPORT","url":"https://bugzilla.redhat.com/show_bug.cgi?id=2488439"},{"type":"PACKAGE","url":"https://github.com/netty/netty"},{"type":"WEB","url":"https://access.redhat.com/errata/RHSA-2026:53806"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-09-20T11:46:04.741662531Z"}}