Package Instance

Puma HTTP Request/Response Smuggling vulnerability
### Impact
Prior to versions 6.4.2 and 5.6.8, puma exhibited dangerous behavior when parsing chunked transfer encoding bodies.

Fixed versions limit the size of chunk extensions. Without this limit, an attacker could cause unbounded resource (CPU, network bandwidth) consumption.

### Patches

The vulnerability has been fixed in 6.4.2 and 5.6.8.

### Workarounds

No known workarounds.

### References

* [HTTP Request Smuggling](https://portswigger.net/web-security/request-smuggling)
* Open an issue in [Puma](https://github.com/puma/puma)
* See our [security policy](https://github.com/puma/puma/security/policy)

Puma's header normalization allows for client to clobber proxy set headers
### Impact

Clients could clobber values set by intermediate proxies (such as X-Forwarded-For) by providing a underscore version of the same header (X-Forwarded_For). Any users trusting headers set by their proxy may be affected. Attackers may be able to downgrade connections to HTTP (non-SSL) or redirect responses, which could cause confidentiality leaks if combined with a separate MITM attack. 

### Patches
v6.4.3/v5.6.9 now discards any headers using underscores if the non-underscore version also exists. Effectively, allowing the proxy defined headers to always win.

### Workarounds
Nginx has a [underscores_in_headers](https://nginx.org/en/docs/http/ngx_http_core_module.html#underscores_in_headers) configuration variable to discard these headers at the proxy level.

Any users that are implicitly trusting the proxy defined headers for security or availability should immediately cease doing so until upgraded to the fixed versions.