CVE-2021-21409Published

Possible request smuggling in HTTP/2 due missing validation of content-length

Exact source revision recorded 23 Oct 2026 15:48:27 UTC. It does not establish the source's current position. Latest evidence.

Recorded JSON

cve-program · CVE-2021-21409

Published

Netty is an open-source, asynchronous event-driven network application framework for rapid development of maintainable high performance protocol servers & clients. In Netty (io.netty:netty-codec-http2) before version 4.1.61.Final there is a vulnerability that enables request smuggling. The content-length header is not correctly validated if the request only uses a single Http2HeaderFrame with the endStream set to to true. This could lead to request smuggling if the request is proxied to a remote peer and translated to HTTP/1.1. This is a followup of GHSA-wm47-8v5p-wjpj/CVE-2021-21295 which did miss to fix this one case. This was fixed as part of 4.1.61.Final.

Source published: 30 Mar 2021 15:05:17 UTC
Source modified: 8 Oct 2026 21:13:55 UTC
Observed here: 23 Oct 2026 15:48:27 UTC
Source terms: CVE Program Terms of Use

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CVSS 3.1 · 5.9 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N