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CVE-2021-21295

Publication date 9 March 2021

Last updated 24 July 2024

Ubuntu priority

Medium

Why this priority?

Cvss 3 Severity Score

5.9 · Medium

Score breakdown

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`.

Status

Package Ubuntu Release Status
netty 24.10 oracular
Needs evaluation
24.04 LTS noble
Needs evaluation
23.10 mantic Ignored end of life, was needs-triage
23.04 lunar Ignored end of life, was needs-triage
22.10 kinetic
Fixed 1:4.1.48-5ubuntu0.1
22.04 LTS jammy
Fixed 1:4.1.48-4+deb11u1build0.22.04.1
21.10 impish Ignored end of life
21.04 hirsute Ignored end of life
20.10 groovy Ignored end of life
20.04 LTS focal
18.04 LTS bionic
16.04 LTS xenial
14.04 LTS trusty
Needs evaluation

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Severity score breakdown

Parameter Value
Base score 5.9 · Medium
Attack vector Network
Attack complexity High
Privileges required None
User interaction None
Scope Unchanged
Confidentiality None
Integrity impact High
Availability impact None
Vector CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N