GHSA-F3PG-QWVG-P99C Lenient Parsing of Content-Length Header When Prefixed with Plus Sign

Summary hyper's HTTP/1 server code had a flaw that incorrectly parses and accepts requests with a Content-Length header with a prefixed plus sign, when it should have been rejected as illegal. This combined with an upstream HTTP proxy that doesn't parse such Content-Length headers, but forwards...