All versions of the package ithewei/libhv are vulnerable to HTTP Response Splitting when untrusted user input is used to build headers values. An attacker can add the \r\n (carriage return line feeds) characters to end the HTTP response headers and inject malicious content, like for example additional headers or new response body, leading to a potential XSS vulnerability.

A vulnerability in Cisco Email Security Appliance (ESA) and Cisco Secure Email and Web Manager could allow an unauthenticated, remote attacker to conduct an HTTP response splitting attack. This vulnerability is due to the failure of the application or its environment to properly sanitize input values. An attacker could exploit this vulnerability by injecting malicious HTTP headers, controlling the response body, or splitting the response into multiple responses.

Prior to Apache HTTP Server 2.4.55, a malicious backend can cause the response headers to be truncated early, resulting in some headers being incorporated into the response body. If the later headers have any security purpose, they will not be interpreted by the client.