Bug#984948: netty: CVE-2021-21295

[Salvatore Bonaccorso]

Source: netty
Version: 1:4.1.48-2
Severity: important
Tags: security upstream
X-Debbugs-Cc: carnil at debian.org, Debian Security Team <team at security.debian.org>

Hi,

The following vulnerability was published for netty.

CVE-2021-21295[0]:
| 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`.


[1] contains some more details and [2] ist the upstream merge to fix
the issue, not sure if it can be backported to older versions.

If you fix the vulnerability please also make sure to include the
CVE (Common Vulnerabilities & Exposures) id in your changelog entry.

For further information see:

[0] https://security-tracker.debian.org/tracker/CVE-2021-21295
    https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-21295
[1] https://github.com/netty/netty/security/advisories/GHSA-wm47-8v5p-wjpj
[2] https://github.com/netty/netty/commit/89c241e3b1795ff257af4ad6eadc616cb2fb3dc4

Please adjust the affected versions in the BTS as needed.

Regards,
Salvatore