CVE-2021-21295 (Medium) detected in netty-codec-http-4.1.20.Final.jar

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CVE-2021-21295 - Medium Severity Vulnerability

Vulnerable Library - netty-codec-http-4.1.20.Final.jar

Netty is an asynchronous event-driven network application framework for rapid development of maintainable high performance protocol servers and clients.

Library home page: http://netty.io/

Path to vulnerable library: /home/wss-scanner/.ivy2/cache/io.netty/netty-codec-http/jars/netty-codec-http-4.1.20.Final.jar

Dependency Hierarchy:

• async-http-client-2.2.1.jar (Root Library)
  • netty-handler-proxy-4.1.20.Final.jar
    • ❌ netty-codec-http-4.1.20.Final.jar (Vulnerable Library)

Found in base branch: master

Vulnerability Details

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.

Publish Date: 2021-03-09

URL: CVE-2021-21295

CVSS 3 Score Details (5.9)

Base Score Metrics:

• Exploitability Metrics:
  • Attack Vector: Network
  • Attack Complexity: High
  • Privileges Required: None
  • User Interaction: None
  • Scope: Unchanged
• Impact Metrics:
  • Confidentiality Impact: None
  • Integrity Impact: High
  • Availability Impact: None

For more information on CVSS3 Scores, click here.

Suggested Fix

Type: Upgrade version

Origin: GHSA-wm47-8v5p-wjpj

Release Date: 2021-03-09

Fix Resolution: io.netty:netty-codec-http:4.1.60