ruby/webrick

Ruby WEBrick read_header HTTP Request Smuggling Vulnerability. This vulnerability allows remote attackers to smuggle arbitrary HTTP requests on affected installations of Ruby WEBrick. This issue is exploitable when the product is deployed behind an HTTP proxy that fulfills specific conditions. The specific flaw exists within the read_headers method. The issue results from the inconsistent parsing of terminators of HTTP headers. An attacker can leverage this vulnerability to smuggle arbitrary HTTP requests. Was ZDI-CAN-21876.

An issue was discovered in the WEBrick toolkit through 1.8.1 for Ruby. It allows HTTP request smuggling by providing both a Content-Length header and a Transfer-Encoding header, e.g., "GET /admin HTTP/1.1\r\n" inside of a "POST /user HTTP/1.1\r\n" request. NOTE: the supplier's position is "Webrick should not be used in production."

An issue was discovered in Ruby through 2.5.8, 2.6.x through 2.6.6, and 2.7.x through 2.7.1. WEBrick, a simple HTTP server bundled with Ruby, had not checked the transfer-encoding header value rigorously. An attacker may potentially exploit this issue to bypass a reverse proxy (which also has a poor header check), which may lead to an HTTP Request Smuggling attack.