CVE-2026-42579Public exploitNetwork attack vector

DNS cache poisoning via invalid DNS label handling

Published May 13, 2026 · Updated May 13, 2026

Input validation in Netty's DNS codec before 4.1.133.Final and 4.2.0.Alpha1 through 4.2.12.Final allows remote attackers to poison DNS caches. DnsCodecUtil.encodeDomainName() writes null bytes and invalid labels into DNS output, while decodeDomainName() grows output without RFC 1035 label or name-length bounds. The encoder requires user-influenced hostnames; the decoder requires responses from a malicious or compromised DNS server, with integrity effects including differential parsing and domain-validation bypass.

CVSS severity7.5
High
EPSS probability1.01%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Input validation in Netty's DNS codec before 4.1.133.Final and 4.2.0.Alpha1 through 4.2.12.Final allows remote attackers to poison DNS caches. DnsCodecUtil.encodeDomainName() writes null bytes and invalid labels into DNS output, while decodeDomainName() grows output without RFC 1035 label or name-length bounds. The encoder requires user-influenced hostnames; the decoder requires responses from a malicious or compromised DNS server, with integrity effects including differential parsing and domain-validation bypass.

The record

CVE
CVE-2026-42579
Published
May 13, 2026
Updated
May 13, 2026
Vendor
The Netty Project
Product
Netty
Classifications
CWE-20, CWE-400, CWE-626, T1565.001, T1499.003
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 13, 2026CVE publishedPublication date reported by the CVE source.
  2. May 13, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 4.1.133.Final
  2. Affected versionversion=>= 4.2.0.Alpha1, < 4.2.13.Final

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

The Netty Project · Nettyversion=< 4.1.133.Final; version=>= 4.2.0.Alpha1, < 4.2.13.Final

Published CVSS scores

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

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-20Improper Input Validation
CWE-400Uncontrolled Resource Consumption
CWE-626Null Byte Interaction Error (Poison Null Byte)
T1565.001Data Manipulation: Stored Data Manipulation
T1499.003Endpoint Denial of Service: Application Exhaustion Flood

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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