CVE-2026-42584 is a high-severity security vulnerability in io.netty:netty-codec-http (maven), affecting versions >= 4.2.0.Alpha1, <= 4.2.12.Final. It is fixed in 4.2.13.Final, 4.1.133.Final.
Summary If HttpClientCodec is configured, there are use cases when a response body from one request, can be parsed as another's. Details 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. Prerequisites HTTP/1.1 pipelining HEAD in the pipeline The server sends 1xx PoC Impact Integrity/availability of HTTP parsing on that connection, unsafe reuse of the socket.
CVE-2026-42584 has a CVSS score of 7.3 (High). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment.
A fixed version is available (4.2.13.Final, 4.1.133.Final). Upgrading removes the vulnerable code path.
maven
io.netty:netty-codec-http (>= 4.2.0.Alpha1, <= 4.2.12.Final)io.netty:netty-codec-http (<= 4.1.132.Final)io.netty:netty-codec-http → 4.2.13.Final (maven)io.netty:netty-codec-http → 4.1.133.Final (maven)Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter instead of chasing every advisory.
Kodem's runtime-powered SCA identifies whether CVE-2026-42584 is reachable in your applications. Explore open-source security for your team.
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Upgrade the following packages to resolve this vulnerability:
io.netty:netty-codec-http to 4.2.13.Final or laterio.netty:netty-codec-http to 4.1.133.Final or laterKodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.
CVE-2026-42584 is a high-severity security vulnerability in io.netty:netty-codec-http (maven), affecting versions >= 4.2.0.Alpha1, <= 4.2.12.Final. It is fixed in 4.2.13.Final, 4.1.133.Final.
CVE-2026-42584 has a CVSS score of 7.3 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
io.netty:netty-codec-http (maven) versions >= 4.2.0.Alpha1, <= 4.2.12.Final is affected.
Yes. CVE-2026-42584 is fixed in 4.2.13.Final, 4.1.133.Final. Upgrade to this version or later.
Whether CVE-2026-42584 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
io.netty:netty-codec-http to 4.2.13.Final or laterio.netty:netty-codec-http to 4.1.133.Final or later