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Netty Vulnerable to DNS Cache Poisoning via Missing Bailiwick Checks in CNAME Records

High severity GitHub Reviewed Published Jun 5, 2026 in netty/netty • Updated Aug 13, 2026

Package

maven io.netty:netty-resolver-dns (Maven)

Affected versions

>= 4.2.0.Final, <= 4.2.14.Final
<= 4.1.134.Final

Patched versions

4.2.15.Final
4.1.135.Final

Description

Summary

Netty's DnsResolveContext fails to validate the origin (bailiwick) of CNAME records in DNS responses.

Details

In io.netty.resolver.dns.DnsResolveContext#buildAliasMap, the resolver processes the ANSWER section of a DNS response and blindly caches all CNAME records it finds.

According to https://datatracker.ietf.org/doc/html/rfc5452#section-6

Care must be taken to only accept
   data if it is known that the originator is authoritative for the
   QNAME or a parent of the QNAME.
   One very simple way to achieve this is to only accept data if it is
   part of the domain for which the query was intended.

Impact

DNS Cache Poisoning (Bailiwick Bypass). Any application using Netty's DNS resolver is impacted.

References

@chrisvest chrisvest published to netty/netty Jun 5, 2026
Published to the GitHub Advisory Database Jun 8, 2026
Reviewed Jun 8, 2026
Published by the National Vulnerability Database Jun 12, 2026
Last updated Aug 13, 2026

Severity

High

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
High
Privileges required
None
User interaction
None
Scope
Changed
Confidentiality
High
Integrity
High
Availability
None

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:N

EPSS score

Exploit Prediction Scoring System (EPSS)

This score estimates the probability of this vulnerability being exploited within the next 30 days. Data provided by FIRST.
(16th percentile)

Weaknesses

Insufficient Verification of Data Authenticity

The product does not sufficiently verify the origin or authenticity of data, in a way that causes it to accept invalid data. Learn more on MITRE.

Origin Validation Error

The product does not properly verify that the source of data or communication is valid. Learn more on MITRE.

CVE ID

CVE-2026-45674

GHSA ID

GHSA-676x-f7gg-47vc

Source code

Credits

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