Netty has HttpClientCodec response desynchronization

Exploitation

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

CVSS

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

EPSS

• CVE-2026-42584: 0.84% estimated exploitation activity in the next 30 days; percentile 57.82 (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.

Summary If HttpClientCodec is configured, there are use cases when a response body from one request, can be parsed as another's. Details 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. Prerequisites - HTTP/1.1 pipelining - HEAD in the pipeline - The server sends 1xx PoC Impact Integrity/availability of HTTP parsing on that connection, unsafe reuse of the socket.

Published by the source

7 May 2026, 00:21 UTC

Last modified by the source

14 May 2026, 20:41 UTC

Source last checked

26 Oct 2026, 16:45 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-57rv-r2g8-2cj3

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# Patch Next advisory brief: CVE-2026-42584

Advisory: Netty has HttpClientCodec response desynchronization
IDs: CVE-2026-42584, GHSA-57rv-r2g8-2cj3
Record: https://patchnext.com/advisories/cve-2026-42584 (revision 1, source checked 26 Oct 2026, 16:45 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.3)
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-http 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-http: 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-http: 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-http.
- 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-57rv-r2g8-2cj3 (GitHub-reviewed advisory GHSA-57rv-r2g8-2cj3 lists affected ranges: Maven io.netty:netty-codec-http >=4.2.0.Alpha1 =0 <=4.1.132.Final)

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