CVE-2026-42584
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 · uneditedNetty is an asynchronous, event-driven network application framework. Prior to 4.2.13.Final and 4.1.133.Final, HttpClientCodec pairs each inbound response with an outbound request by queue.poll() once per response, including for 1xx. If the client pipelines GET then HEAD and the server sends 103, then 200 with GET body, then 200 for HEAD, the queue pairs HEAD with the first 200. The HEAD rule then skips reading that message’s body, so the GET entity bytes stay on the stream and the following 200 is parsed from the wrong offset. This vulnerability is fixed in 4.2.13.Final and 4.1.133.Final.
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 confidenceIn Netty's HttpClientCodec, response-request pairing uses queue.poll() for ALL responses including 1xx informational responses. When HTTP pipelining GET then HEAD requests, and the server sends 103, then 200 with GET body, then 200 for HEAD, the queue incorrectly pairs HEAD with the first 200. Since HEAD rules skip reading the message body, the GET entity bytes remain on the stream causing subsequent 200 responses to be parsed from incorrect offsets, leading to response parsing corruption.
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< 4.1.133>= 4.2.0, < 4.2.13CVSS 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
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H
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 checksWork through these to decide whether this CVE applies to you.
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Identify Netty version in useInspect your project's dependency manifest (pom.xml, build.gradle, requirements.txt for Java, or list installed Java libraries) to find the netty version. Check for netty-all, io.netty:netty-common, or similar Netty artifacts.Affected if The installed Netty version is below 4.1.133, or is 4.2.0 through 4.2.12 (inclusive).
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Confirm HttpClientCodec is in useSearch your codebase for imports or references to io.netty.handler.codec.http.HttpClientCodec, or look for HttpPipelineBuilder or custom HTTP client configurations that utilize this codec.Affected if Your application uses Netty's HttpClientCodec to handle HTTP responses.
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Determine if HTTP pipelining is enabledReview your HTTP client configuration to see if multiple requests are being sent without waiting for responses (pipelining). Look for settings or code patterns that enable request pipelining on the client side.Affected if Your client sends multiple HTTP requests in sequence without waiting for each response, which is the pipelining pattern.
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Check for 1xx informational response handlingInspect whether your client or server logic involves 103 Early Hints responses or other 1xx informational messages being sent before final responses in pipelined request chains.Affected if Your HTTP interactions involve 1xx informational responses (such as 103 Early Hints) occurring within pipelined request sequences.
You are affected if your Netty version falls within the vulnerable ranges AND your application uses HttpClientCodec with HTTP pipelining that includes 1xx informational responses, causing response pairing to be incorrect.
Generated from the published advisory. Verify against your own configuration.
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 · scoped4.1.1334.2.13
Upgrade Netty to version 4.2.13.Final or 4.1.133.Final or later to fix the HttpClientCodec response queueing logic.
4.1.133.Final or 4.2.13.Final (depending on your major version branch)
- Identify the current Netty version in use (check pom.xml, build.gradle, or dependency management)
- Determine whether the project uses Netty 4.1.x or 4.2.x line
- For 4.1.x users: upgrade to netty 4.1.133.Final
- For 4.2.x users: upgrade to netty 4.2.13.Final
- Update the dependency version in Maven (pom.xml) or Gradle (build.gradle)
- Run mvn clean install or gradle build to fetch the new version
- Rebuild and test the application to ensure the upgrade does not break existing functionality
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation2.0 h
- Implementation2.0 h
- Testing4.0 h
- Review / QA1.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,464.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-42584 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-42584 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Version or environment caveats, and links to real fixes
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