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GHSA-wm47-8v5p-wjpj

Dashboard / Vulnerabilities / GHSA-wm47-8v5p-wjpj

GHSA-wm47-8v5p-wjpj

Published: 9 Mar 2021Last Modified: 10 Sept 2026

Aliases:

CVE-2021-21409

Summary: Possible request smuggling in HTTP/2 due missing validation

Details: ### Impact 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. A sample attack request looks like: ``` POST / HTTP/2 :authority:: externaldomain.com Content-Length: 4 asdfGET /evilRedirect HTTP/1.1 Host: internaldomain.com ``` 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 * These HTTP/1.1 objects are forwarded to another remote peer. ### Patches This has been patched in 4.1.60.Final ### Workarounds The user can do the validation by themselves by implementing a custom `ChannelInboundHandler` that is put in the `ChannelPipeline` behind `Http2StreamFrameToHttpObjectCodec`. ### References Related change to workaround the problem: https://github.com/Netflix/zuul/pull/980

Affected packages

Package

Name: io.netty:netty-codec-http2

Purl: pkg:maven/io.netty/netty-codec-http2

Affected ranges

Type: ECOSYSTEM

Events:

Introduced- 4.0.0

Fixed -4.1.60.Final

Affected versions

4.1.0.Beta4

4.1.0.Beta5

4.1.0.Beta6

4.1.0.Beta7

4.1.0.Beta8

4.1.0.CR1

4.1.0.CR2

4.1.0.CR3

4.1.0.CR4

4.1.0.CR5

4.1.0.CR6

4.1.0.CR7

4.1.0.Final

4.1.1.Final

4.1.10.Final

4.1.11.Final

4.1.12.Final

4.1.13.Final

4.1.14.Final

4.1.15.Final

4.1.16.Final

4.1.17.Final

4.1.18.Final

4.1.19.Final

4.1.2.Final

4.1.20.Final

4.1.21.Final

4.1.22.Final

4.1.23.Final

4.1.24.Final

4.1.25.Final

4.1.26.Final

4.1.27.Final

4.1.28.Final

4.1.29.Final

4.1.3.Final

4.1.30.Final

4.1.31.Final

4.1.32.Final

4.1.33.Final

4.1.34.Final

4.1.35.Final

4.1.36.Final

4.1.37.Final

4.1.38.Final

4.1.39.Final

4.1.4.Final

4.1.40.Final

4.1.41.Final

4.1.42.Final

4.1.43.Final

4.1.44.Final

4.1.45.Final

4.1.46.Final

4.1.47.Final

4.1.48.Final

4.1.49.Final

4.1.5.Final

4.1.50.Final

4.1.51.Final

4.1.52.Final

4.1.53.Final

4.1.54.Final

4.1.55.Final

4.1.56.Final

4.1.57.Final

4.1.58.Final

4.1.59.Final

4.1.6.Final

4.1.7.Final

4.1.8.Final

4.1.9.Final

Common Vulnerability Scoring System

Attack Vector

Network

Adjacent

Local

Physical

Privileges Required

None

Low

High

User Interaction

None

Required

Scope

Unchanged

Changed

Confidentiality

None

Low

High

Integrity

None

Low

High

Availability

None

Low

High