Netty vulnerable to request smuggling due to incorrect parsing of chunk extensions

Exploitation

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

CVSS

not scored

EPSS

• CVE-2025-58056: 0.71% estimated exploitation activity in the next 30 days; percentile 53.58 (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 A flaw in netty's parsing of chunk extensions in HTTP/1.1 messages with chunked encoding can lead to request smuggling issues with some reverse proxies. Details When encountering a newline character (LF) while parsing a chunk extension, netty interprets the newline as the end of the chunk-size line regardless of whether a preceding carriage return (CR) was found. This is in violation of the HTTP 1.1 standard which specifies that the chunk extension is terminated by a CRLF sequence (see the RFC). This is by itself harmless, but consider an intermediary with a similar parsing flaw: while parsing a chunk extension, the intermediary interprets an LF without a preceding CR as simply part of the chunk extension (this is also in violation of the RFC, because whitespace characters are not allowed in chunk extensions). We can use this discrepancy to construct an HTTP request that the intermediary will interpret as one request but netty will interpret as two (all lines ending with…

Published by the source

4 Sep 2025, 17:35 UTC

Last modified by the source

10 Sep 2025, 20:48 UTC

Source last checked

26 Oct 2026, 16:39 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-fghv-69vj-qj49

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: CVE-2025-58056

Advisory: Netty vulnerable to request smuggling due to incorrect parsing of chunk extensions
IDs: CVE-2025-58056, GHSA-fghv-69vj-qj49
Record: https://patchnext.com/advisories/cve-2025-58056 (revision 1, source checked 26 Oct 2026, 16:39 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Unrated
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 4.2.5.Final, 4.1.125.Final. A vendor fix does not mean a deployment is fixed.

## Affected components
- Maven io.netty:netty-codec-http: affected < 4.1.125.Final; >= 4.2.0.Alpha1, < 4.2.5.Final; fixed in 4.2.5.Final, 4.1.125.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-fghv-69vj-qj49 (GitHub-reviewed advisory GHSA-fghv-69vj-qj49 lists affected ranges: Maven io.netty:netty-codec-http >=0 =4.2.0.Alpha1 <4.2.5.Final)

Commands are suggestions: review each one before running it.