There is a vulnerability in Apache Traffic Server (ATS) 6.2.0 and prior and 7.0.0 and prior with the Host header and line folding. This can have issues when interacting with upstream proxies and the wrong host being used.

Undertow in Red Hat wildfly before version 11.0.0.Beta1 is vulnerable to a resource exhaustion resulting in a denial of service. Undertow keeps a cache of seen HTTP headers in persistent connections. It was found that this cache can easily exploited to fill memory with garbage, up to "max-headers" (default 200) * "max-header-size" (default 1MB) per active TCP connection.

PHP through 7.1.11 enables potential SSRF in applications that accept an fsockopen or pfsockopen hostname argument with an expectation that the port number is constrained. Because a :port syntax is recognized, fsockopen will use the port number that is specified in the hostname argument, instead of the port number in the second argument of the function.