Netty has a DNS Codec Input Validation Bypass (Encoder + Decoder)

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

7.5 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

EPSS

• CVE-2026-42579: 1.01% estimated exploitation activity in the next 30 days; percentile 63.06 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Security Vulnerability Report: DNS Codec Input Validation Bypass in Netty (Encoder + Decoder) 1. Vulnerability Summary | Field | Value | |-------|-------| | Product | Netty | | Version | 4.2.12.Final (and all prior versions with codec-dns) | | Component | io.netty.handler.codec.dns.DnsCodecUtil | | Vulnerability Type | CWE-20: Improper Input Validation / CWE-626: Null Byte Interaction Error / CWE-400: Uncontrolled Resource Consumption | | Impact | DNS Cache Poisoning / Domain Validation Bypass / Denial of Service / Malformed DNS Packets | 2. Affected Components Both the encoder and decoder in the same file are affected: - io.netty.handler.codec.dns.DnsCodecUtil — encodeDomainName() method (lines 31-51): - No null byte validation in domain name labels - No per-label length validation (RFC 1035 max: 63 bytes) - No total domain name length validation (RFC 1035 max: 255 bytes) - Empty labels silently truncate the domain name - io.netty.handler.codec.dns.DnsCodecUtil — decodeDomainName()…

Published by the source

7 May 2026, 00:12 UTC

Last modified by the source

11 Jun 2026, 10:04 UTC

Source last checked

26 Oct 2026, 16:46 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-cm33-6792-r9fm

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# Patch Next advisory brief: CVE-2026-42579

Advisory: Netty has a DNS Codec Input Validation Bypass (Encoder + Decoder)
IDs: CVE-2026-42579, GHSA-cm33-6792-r9fm
Record: https://patchnext.com/advisories/cve-2026-42579 (revision 1, source checked 26 Oct 2026, 16:46 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: io.netty:netty-codec-dns 4.2.13.Final, 4.1.133.Final. A vendor fix does not mean a deployment is fixed.

## Affected components
- Maven io.netty:netty-codec-dns: affected >= 4.2.0.Alpha1, <= 4.2.12.Final; <= 4.1.132.Final; fixed in 4.2.13.Final, 4.1.133.Final

## Suggested inspection (read-only)
- Maven io.netty:netty-codec-dns: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on io.netty:netty-codec-dns.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-cm33-6792-r9fm (GitHub-reviewed advisory GHSA-cm33-6792-r9fm lists affected ranges: Maven io.netty:netty-codec-dns >=4.2.0.Alpha1 =0 <=4.1.132.Final)

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