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CVE-2026-42581

Netty: HTTP/1.0 TE+CL Coexistence Bypasses Smuggling Sanitization

CVSS 3.1 5.8 MEDIUMCheck source for fixed versionsKEV status unknown

Original advisory

cve-program · CVE-2026-42581

Published

Netty is an asynchronous, event-driven network application framework. Prior to 4.2.13.Final and 4.1.133.Final, HttpObjectDecoder strips a conflicting Content-Length header when a request carries both Transfer-Encoding: chunked and Content-Length, but only for HTTP/1.1 messages. The guard is absent for HTTP/1.0. An attacker that sends an HTTP/1.0 request with both headers causes Netty to decode the body as chunked while leaving Content-Length intact in the forwarded HttpMessage. Any downstream proxy or handler that trusts Content-Length over Transfer-Encoding will disagree on message boundaries, enabling request smuggling. This vulnerability is fixed in 4.2.13.Final and 4.1.133.Final.

Read the publisher's advisory

Affected versions, risk and source history

cve-program · CVE-2026-42581

Published

netty

Vendor product

Publisher's version information

Shown as published. These rules are not interpreted as NuGet package version ranges.

{
                    "vendor": "netty",
                    "product": "netty",
                    "versions": [
                        {
                            "version": ">= 4.2.0.Alpha1, < 4.2.13.Final",
                            "status": "affected"
                        },
                        {
                            "version": "< 4.1.133.Final",
                            "status": "affected"
                        }
                    ]
                }

Original source record · Cite this exact observation · Complete original publisher JSON