Netty: HTTP Request Smuggling via Chunked Extension Quoted-String Parsing

Exploitation

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

CVSS

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

EPSS

• CVE-2026-33870: 0.70% estimated exploitation activity in the next 30 days; percentile 53.26 (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 Netty incorrectly parses quoted strings in HTTP/1.1 chunked transfer encoding extension values, enabling request smuggling attacks. Background This vulnerability is a new variant discovered during research into the "Funky Chunks" HTTP request smuggling techniques: - <https://w4ke.info/2025/06/18/funky-chunks.html - <https://w4ke.info/2025/10/29/funky-chunks-2.html The original research tested various chunk extension parsing differentials but did not cover quoted-string handling within extension values. Technical Details RFC 9110 Section 7.1.1 defines chunked transfer encoding: RFC 9110 Section 5.6.4 defines quoted-string: Critically, the allowed character ranges within a quoted-string are: CR (%x0D) and LF (%x0A) bytes fall outside all of these ranges and are therefore not permitted inside chunk extensions—whether quoted or unquoted. A strictly compliant parser should reject any request containing CR or LF bytes before the actual line terminator within a chunk extension with…

Published by the source

26 Mar 2026, 18:48 UTC

Last modified by the source

27 Mar 2026, 21:49 UTC

Source last checked

26 Oct 2026, 16:44 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-pwqr-wmgm-9rr8

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

# Patch Next advisory brief: CVE-2026-33870

Advisory: Netty: HTTP Request Smuggling via Chunked Extension Quoted-String Parsing
IDs: CVE-2026-33870, GHSA-pwqr-wmgm-9rr8
Record: https://patchnext.com/advisories/cve-2026-33870 (revision 1, source checked 26 Oct 2026, 16:44 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.5)
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 4.2.10.Final, 4.1.132.Final. A vendor fix does not mean a deployment is fixed.

## Affected components
- Maven io.netty:netty-codec-http: affected < 4.1.132.Final; >= 4.2.0.Alpha1, < 4.2.10.Final; fixed in 4.1.132.Final, 4.2.10.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-pwqr-wmgm-9rr8 (GitHub-reviewed advisory GHSA-pwqr-wmgm-9rr8 lists affected ranges: Maven io.netty:netty-codec-http >=0 =4.2.0.Alpha1 <4.2.10.Final)

Commands are suggestions: review each one before running it.