Netty has Insufficient Bailiwick Validation for NS Records
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.
Affected software
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| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| Java / Kotlin (Maven) | io.netty:netty-resolver-dns | >= 4.2.0.Final, < 4.2.15.Final, < 4.1.135.Final | 4.2.15.Final, 4.1.135.Final |
References
- https://github.com/netty/netty/security/advisories/GHSA-5pvg-856g-cp85
- https://nvd.nist.gov/vuln/detail/CVE-2026-47691
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-47691.json
- https://github.com/netty/netty/releases/tag/netty-4.2.15.Final
- https://github.com/netty/netty/releases/tag/netty-4.1.135.Final
- https://github.com/netty/netty
- https://bugzilla.redhat.com/show_bug.cgi?id=2488439
- https://access.redhat.com/security/cve/CVE-2026-47691
- https://access.redhat.com/errata/RHSA-2026:65126
- https://access.redhat.com/errata/RHSA-2026:62260
- https://access.redhat.com/errata/RHSA-2026:54435
- https://access.redhat.com/errata/RHSA-2026:53806
- https://access.redhat.com/errata/RHSA-2026:53646
- https://access.redhat.com/errata/RHSA-2026:53645
- https://access.redhat.com/errata/RHSA-2026:53644
- https://access.redhat.com/errata/RHSA-2026:50085
- https://access.redhat.com/errata/RHSA-2026:49701
- https://access.redhat.com/errata/RHSA-2026:49700
- https://access.redhat.com/errata/RHSA-2026:48151
- https://access.redhat.com/errata/RHSA-2026:41951
- https://access.redhat.com/errata/RHSA-2026:37390
- https://access.redhat.com/errata/RHSA-2026:34608
- https://access.redhat.com/errata/RHSA-2026:26586
- https://access.redhat.com/errata/RHSA-2026:26018
- https://access.redhat.com/errata/RHSA-2026:26017
- CVSS vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:N- Weakness (CWE)
CWE-345, CWE-346- Platform
- Java / Kotlin (Maven)
- Package
io.netty:netty-resolver-dns- Disclosed
- 08.06.2026
- Updated
- 11.10.2026 13:20
Sources and licenses
OSV / GitHub Advisory Database - GHSA-5pvg-856g-cp85 - CC BY 4.0
Vulnerability history: io.netty:netty-resolver-dns
All published vulnerabilities of this package (Java / Kotlin (Maven)), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 3
- First → latest
- 06.2026 06.2026
- Without a fix
- 0
- Exploited in attacks
- 0
Severity breakdown
- High 2
- Medium 1
Disclosures per year
- 2026: 3
-
Netty has Insufficient Bailiwick Validation for NS Records this entry
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