CVE-2021-21295

Inconsistent Interpretation of HTTP Requests (HTTP Request Smuggling) in maven/io.netty/netty-codec-http2

Identifier

CVE-2021-21295

Package Slug

maven/io.netty/netty-codec-http2

Vulnerability

Inconsistent Interpretation of HTTP Requests (HTTP Request Smuggling)

Description

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. 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. 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 Versions

All versions before 4.1.60

Solution

Upgrade to version 4.1.60.Final or above.

Last Modified

2021-03-29

source