CVE-2026-42584 — Netty: HttpClientCodec response desynchronization

Description (CNA)

Netty is an asynchronous, event-driven network application framework. Prior to 4.2.13.Final and 4.1.133.Final, 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. This vulnerability is fixed in 4.2.13.Final and 4.1.133.Final.

Affected (CNA)

Vendor / product	Versions
netty / netty	affected >= 4.2.0.Alpha1, < 4.2.13.Final; affected < 4.1.133.Final
io.netty / netty-codec-http	affected >= 4.2.0.Alpha1, < 4.2.13.Final; affected < 4.1.133.Final

CWE

CWE-444

References

https://github.com/netty/netty/security/advisories/GHSA-57rv-r2g8-2cj3

ADP enrichment

CISA-ADP

No English description supplied.

https://github.com/netty/netty/security/advisories/GHSA-57rv-r2g8-2cj3

redhat-SADP

A flaw was found in Netty, an asynchronous, event-driven network application framework. A remote attacker could exploit this vulnerability by sending a specific sequence of HTTP responses (103, followed by a 200 with a GET body, then another 200 for a HEAD request) when the client pipelines GET then HEAD requests. This can cause the HttpClientCodec to incorrectly pair responses, leading to subsequent HTTP responses being parsed from the wrong offset. This issue may result in information disclosure or other data integrity problems due to misinterpretation of network traffic.