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Security Advisories: MDE2OlNlY3VyaXR5QWR2aXNvcnlHSFNBLXdtNDctOHY1cC13anBq

Possible request smuggling in HTTP/2 due missing validation

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:

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

Permalink: https://github.com/advisories/GHSA-wm47-8v5p-wjpj
JSON: https://advisories.ecosyste.ms/api/v1/advisories/MDE2OlNlY3VyaXR5QWR2aXNvcnlHSFNBLXdtNDctOHY1cC13anBq
Source: GitHub Advisory Database
Origin: Unspecified
Severity: Moderate
Classification: General
Published: about 3 years ago
Updated: 9 months ago


CVSS Score: 5.9
CVSS vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N

Identifiers: GHSA-wm47-8v5p-wjpj, CVE-2021-21295
References: Repository: https://github.com/netty/netty
Blast Radius: 24.6

Affected Packages

maven:io.netty:netty
Dependent packages: 1,133
Dependent repositories: 14,650
Downloads:
Affected Version Ranges: < 4.0.0
No known fixed version
All affected versions:
maven:org.jboss.netty:netty
Dependent packages: 324
Dependent repositories: 1,820
Downloads:
Affected Version Ranges: < 4.0.0
No known fixed version
All affected versions:
maven:io.netty:netty-codec-http2
Dependent packages: 556
Dependent repositories: 1,457
Downloads:
Affected Version Ranges: >= 4.0.0, < 4.1.60.Final
Fixed in: 4.1.60.Final
All affected versions:
All unaffected versions: