CVE-2021-21295: Apache Kudu

Medium severity, CVSS 5.9. EPSS: 18.9% chance of exploitation in the next 30 days.

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 4.1.60.Final there is a vulnerability that enables request smuggling. If a Content-Length header is present in the original HTTP/2 request, the field is not validated by `Http2MultiplexHandler` as it is propagated up. This is fine as long as the request is not proxied through as HTTP/1.1. If the request comes in as an HTTP/2 stream, gets converted into the HTTP/1.1 domain objects (`HttpRequest`, `HttpContent`, etc.) via `Http2StreamFrameToHttpObjectCodec `and then sent up to the child channel's pipeline and proxied through a remote peer as HTTP/1.1 this may result in request smuggling. In a proxy case, users may assume the content-length is validated somehow, which is not the case. If the request is forwarded to a backend channel that is a HTTP/1.1 connection, the Content-Length now has meaning and needs to be checked. An attacker can smuggle requests inside the body as it gets downgraded from HTTP/2 to HTTP/1.1. For an example attack refer to the linked GitHub Advisory. Users are only affected if all of this is true: `HTTP2MultiplexCodec` or `Http2FrameCodec` is used, `Http2StreamFrameToHttpObjectCodec` is used to convert to HTTP/1.1 objects, and these HTTP/1.1 objects are forwarded to another remote peer. This has been patched in 4.1.60.Final As a workaround, the user can do the validation by themselves by implementing a custom `ChannelInboundHandler` that is put in the `ChannelPipeline` behind `Http2StreamFrameToHttpObjectCodec`.

Affected products

  • Apache Kudu: before 1.16.0 (fixed in 1.16.0)
  • Apache Zookeeper: version 3.5.9 only
  • Debian Debian Linux: version 10.0 only
  • Netapp Oncommand API Services: affected versions not specified
  • Netapp Oncommand Workflow Automation: affected versions not specified
  • Netty Netty: before 4.1.60 (fixed in 4.1.60)
  • Oracle Communications Cloud Native Core Policy: version 1.14.0 only
  • Quarkus Quarkus: up to and including 1.13.7

Published 2021-03-09. Last modified 2026-10-08.