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NettyApplication

CVE-2026-45673

MEDIUM · 6.8 CVSS v3.1 Published 2026-06-12
Fix available
A fix is available. Upgrade to 4.1.135 / 4.2.15 or later.
See remediation →
77/100
Remediation priority · High
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
Netty is a network application framework for development of protocol servers and clients. Prior to versions 4.1.135.Final and 4.2.15.Final, Netty's DNS resolver uses a predictable PRNG for generating DNS transaction IDs and defaults to a static UDP source port. This combination reduces the entropy of DNS queries, enabling DNS Cache Poisoning (Kaminsky attack). Versions 4.1.135.Final and 4.2.15.Final patch the issue.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

Netty's DNS resolver prior to versions 4.1.135.Final and 4.2.15.Final uses a predictable pseudo-random number generator (PRNG) for DNS transaction IDs combined with a static UDP source port, which significantly reduces entropy and enables DNS Cache Poisoning (Kaminsky attack).

MitigationUpgrade Netty to version 4.1.135.Final or 4.2.15.Final which implements cryptographically secure random generation for DNS transaction IDs and randomized UDP source ports.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
NettyApplication
Affected:< 4.1.135>= 4.2.0, < 4.2.15

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
High
Privileges
None
User interaction
None
Scope
Changed
Confidentiality
None
Integrity
High
Availability
None

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:H/A:N

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify Netty DNS resolver in use
    Search your codebase for imports of Netty DNS resolver classes such as io.netty.resolver.dns.DnsNameResolver or io.netty.resolver.dns.DnsResolver, or check your dependency manifest (pom.xml, build.gradle, requirements.txt, JAR files) for netty dependencies that include resolver-dns
    Affected if Netty's DNS resolver classes are present in the application dependencies or code
  2. Determine installed Netty version
    Locate the netty-common or resolver-dns JAR file in your classpath, or check your dependency lock file (pom.xml, package-lock.json, gradle.lock) for the exact netty version number
    Affected if The Netty version is below 4.1.135.Final or is 4.2.0 through 4.2.14.Final
  3. Verify DNS queries are processed through Netty
    Review application code for creation of DnsNameResolver or DnsResolver instances, and check runtime logs or configuration for DNS query behavior using Netty's resolver
    Affected if The application creates and uses a Netty DnsNameResolver or DnsResolver instance to perform DNS lookups
  4. Confirm UDP source port behavior
    Capture network traffic during DNS resolution using tcpdump or Wireshark, filter for UDP packets from your Netty application to port 53, and observe whether the source port is static or changes between queries
    Affected if The UDP source port remains identical across multiple DNS queries from the same process

You are affected if your application uses Netty's DNS resolver with a version prior to 4.1.135.Final or between 4.2.0 and 4.2.14.Final, and performs DNS lookups using the vulnerable resolver implementation.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 4.1.135 / 4.2.15 or later
Fixed in 4.1.1354.2.15
Interim mitigation

Upgrade Netty to version 4.1.135.Final or 4.2.15.Final which implements cryptographically secure random generation for DNS transaction IDs and randomized UDP source ports.

Recommended fix High confidence

4.1.135.Final (for 4.1.x branch) or 4.2.15.Final (for 4.2.x branch)

  1. Identify the current Netty version in use by checking project dependencies (e.g., pom.xml, build.gradle, or equivalent)
  2. Determine which Netty branch is being used (4.1.x or 4.2.x)
  3. For Netty 4.1.x users: upgrade to version 4.1.135.Final
  4. For Netty 4.2.x users: upgrade to version 4.2.15.Final
  5. Update the dependency version in the build configuration file
  6. Rebuild and test the application to ensure compatibility

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Netty Scoped from the published advisory
  • Consultation1.0 h
  • Implementation2.0 h
  • Testing2.0 h
  • Review / QA1.0 h
6.0 hours of engineering $1,040
Get the upgrade done

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Scan for this in your stack

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-45673 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data