CVE-2026-33870: Netty: HTTP Request Smuggling via Chunked Extension Quoted-String Parsing

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.7% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2026-03-27 · updated 2026-09-14
Weakness: CWE-444

Description

Netty is an asynchronous, event-driven network application framework. In versions prior to 4.1.132.Final and 4.2.10.Final, Netty incorrectly parses quoted strings in HTTP/1.1 chunked transfer encoding extension values, enabling request smuggling attacks. Versions 4.1.132.Final and 4.2.10.Final fix the issue.

Affected products

netty: before 4.1.132; from 4.2.0 before 4.2.10 — fixed in 4.1.132, 4.2.10

How to fix

Upgrade to a fixed version: netty 4.1.132, 4.2.10. Check the vendor advisory for mitigations.

References

https://github.com/netty/netty/security/advisories/GHSA-pwqr-wmgm-9rr8
https://w4ke.info/2025/06/18/funky-chunks.html
https://w4ke.info/2025/10/29/funky-chunks-2.html
https://www.rfc-editor.org/rfc/rfc9110
https://access.redhat.com/errata/RHSA-2026:10175
https://access.redhat.com/errata/RHSA-2026:10184
https://access.redhat.com/errata/RHSA-2026:13571
https://access.redhat.com/errata/RHSA-2026:14272
https://access.redhat.com/errata/RHSA-2026:14276
https://access.redhat.com/errata/RHSA-2026:17668
https://access.redhat.com/errata/RHSA-2026:17789
https://access.redhat.com/errata/RHSA-2026:18054

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