Package Instance

Puma with proxy which forwards LF characters as line endings could allow HTTP request smuggling
Prior to `puma` version 5.5.0, using `puma` with a proxy which forwards LF characters as line endings could allow HTTP request smuggling. A client could smuggle a request through a proxy, causing the proxy to send a response back to another unknown client.

This behavior (forwarding LF characters as line endings) is very uncommon amongst proxy servers, so we have graded the impact here as "low". Puma is only aware of a single proxy server which has this behavior.

If the proxy uses persistent connections and the client adds another request in via HTTP pipelining, the proxy may mistake it as the first request's body. Puma, however, would see it as two requests, and when processing the second request, send back a response that the proxy does not expect. If the proxy has reused the persistent connection to Puma to send another request for a different client, the second response from the first client will be sent to the second client.

HTTP Response Splitting (Early Hints) in Puma
### Impact
If an application using Puma allows untrusted input in an early-hints header, an attacker can use a carriage return character to end the header and inject malicious content, such as additional headers or an entirely new response body. This vulnerability is known as [HTTP Response Splitting](https://owasp.org/www-community/attacks/HTTP_Response_Splitting).

While not an attack in itself, response splitting is a vector for several other attacks, such as cross-site scripting (XSS).

This is related to [CVE-2020-5247](https://github.com/puma/puma/security/advisories/GHSA-84j7-475p-hp8v), which fixed this vulnerability but only for regular responses.

### Patches
This has been fixed in 4.3.3 and 3.12.4.

### Workarounds
Users can not allow untrusted/user input in the Early Hints response header.

### For more information
If you have any questions or comments about this advisory:
* Open an issue in [puma](https://github.com/puma/puma)
* Email us a project maintainer. [Email addresses are listed in our Code of Conduct](https://github.com/puma/puma/blob/master/CODE_OF_CONDUCT.md#enforcement).

Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')
Puma is a Ruby/Rack web server built for parallelism. Prior to versions 6.3.1 and 5.6.7, puma exhibited incorrect behavior when parsing chunked transfer encoding bodies and zero-length Content-Length headers in a way that allowed HTTP request smuggling. Severity of this issue is highly dependent on the nature of the web site using puma is. This could be caused by either incorrect parsing of trailing fields in chunked transfer encoding bodies or by parsing of blank/zero-length Content-Length headers. Both issues have been addressed and this vulnerability has been fixed in versions 6.3.1 and 5.6.7. Users are advised to upgrade. There are no known workarounds for this vulnerability.

Inconsistent Interpretation of HTTP Requests ('HTTP Request Smuggling')
Puma is a simple, fast, multi-threaded, parallel HTTP 1.1 server for Ruby/Rack applications. When using Puma behind a proxy that does not properly validate that the incoming HTTP request matches the RFC7230 standard, Puma and the frontend proxy may disagree on where a request starts and ends. This would allow requests to be smuggled via the front-end proxy to Puma. The vulnerability has been fixed in 5.6.4 and 4.3.12. Users are advised to upgrade as soon as possible. Workaround: when deploying a proxy in front of Puma, turning on any and all functionality to make sure that the request matches the RFC7230 standard.

Exposure of information in Action Pack
Action Pack is a framework for handling and responding to web requests. Under certain circumstances response bodies will not be closed. In the event a response is *not* notified of a `close`, `ActionDispatch::Executor` will not know to reset thread local state for the next request. This can lead to data being leaked to subsequent requests. This has been fixed in Rails 7.0.2.1, 6.1.4.5, 6.0.4.5, and 5.2.6.1. Upgrading is highly recommended, but to work around this problem a middleware described in GHSA-wh98-p28r-vrc9 can be used.