Contents
What is the HTTP Host header used for?
The Host request header specifies the host and port number of the server to which the request is being sent. If no port is included, the default port for the service requested (e.g., 443 for an HTTPS URL, and 80 for an HTTP URL) is implied. A Host header field must be sent in all HTTP/1.1 request messages.
What is Host attack?
A Host header attack, also known as Host header injection, is a web attack where the attacker provides a false Host header to the web application. Find more information about other types of injection attacks.
What is Crlf attack?
CRLF injection is a software application coding vulnerability that occurs when an attacker injects a CRLF character sequence where it is not expected. When CRLF injection is used to split an HTTP response header, it is referred to as HTTP Response Splitting.
Why are there so many HTTP request smuggling vulnerabilities?
HTTP request smuggling vulnerabilities arise when the frontend and the backend interpret the boundary of an HTTP request differently causing desynchronization between them. This is due to numerous frontend and backend libraries deviating from RFC specifications when dealing with both the Content-Length and the Transfer-Encoding header.
What does the body of an HTTP request mean?
HTTP requests can have a message body. The presence of a message body in a request is signaled by a Content-Length or Transfer-Encoding header field. These headers are used for message framing, telling a server where a message ends and another begins.
What can a smuggled HTTP request be used for?
In a real attack scenario, a smuggled request can be crafted to conduct phishing attacks, or steal data from a victim’s request and send that to an attacker-controlled server.
Is it dangerous to use Host header in PHP?
The use of the host header is especially common in PHP web applications, however, it’s certainly not a problem endemic to PHP web applications. The PHP script in the following example is a typical and dangerous use of the host header.