Advisory details:
github_osv / GHSA-wm47-8v5p-wjpj
| Advisory ID | github_osv/GHSA-wm47-8v5p-wjpj |
| Aliases |
CVE-2021-21295
|
| Summary | 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`: * `HTTP2MultiplexCodec` or `Http2FrameCodec` is used * `Http2StreamFrameToHttpObjectCodec` is used to convert to HTTP/1.1 objects * These HTTP/1.1 objects are forwarded to another remote peer. ### 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 |
| Status | Published |
| Exploitability | 0.5 |
| Weighted Severity | 5.3 |
| Risk | 2.6 |
| Affected and Fixed Packages | Package Details |
| Introduced and Fixed Package Commit Patches | Package Commit Patches Details |
| System | Score | Found at |
|---|---|---|
| cvssv3.1 | 5.9 | https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2021/03/GHSA-wm47-8v5p-wjpj/GHSA-wm47-8v5p-wjpj.json |
| generic_textual | MODERATE |
No EPSS data available for this advisory.
| Patch URL | |
|---|---|
| There are no known patches. | |
| Attack Vector (AV) | Attack Complexity (AC) | Privileges Required (PR) | User Interaction (UI) | Scope (S) | Confidentiality Impact (C) | Integrity Impact (I) | Availability Impact (A) |
|---|---|---|---|---|---|---|---|
network adjacent_network local physical |
low high |
none low high |
none required |
unchanged changed |
high low none |
high low none |
high low none |
There are no SSVC decisions available.