CVE-2026-42584

Description

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.

How to fix CVE-2026-42584

To remediate CVE-2026-42584, upgrade the affected package to a fixed version below.

• —no fix listed
• —upgrade to 4.2.13.Final or later

Is CVE-2026-42584 being exploited?

Low — EPSS is 0.0%, meaning exploitation activity has not been observed at scale.

Affected packages (2)

• from 0
• >= 4.2.0.Alpha1, < 4.2.13.Final

CVSS scores

References (4)

• ADVISORYnvd.nist.gov/vuln/detail/CVE-2026-42584
• ADVISORYsecurity-tracker.debian.org/tracker/CVE-2026-42584
• PATCHgithub.com/netty/netty
• WEBgithub.com/netty/netty/security/advisories/GHSA-57rv-r2g8-2cj3