Execution Flow

Survey network to identify target: The adversary performs network reconnaissance by monitoring relevant traffic to identify the network path and parsing of the HTTP messages with the goal of identifying potential targets.

Techniques
Scan networks to fingerprint HTTP infrastructure and monitor HTTP traffic to identify HTTP network path with a tool such as a Network Protocol Analyzer.

Identify vulnerabilities in targeted HTTP infrastructure and technologies: The adversary sends a variety of benign/ambiguous HTTP requests to observe responses from HTTP infrastructure in order to identify differences/discrepancies in the interpretation and parsing of HTTP requests by examining supported HTTP protocol versions, HTTP headers, syntax checking and input filtering.
Cause differential HTTP responses by experimenting with identified HTTP Request vulnerabilities: The adversary sends maliciously crafted HTTP requests with custom strings and embedded web scripts and objects in HTTP headers to interfere with the parsing of intermediary and back-end HTTP infrastructure, followed by normal/benign HTTP request from the adversary or a random user. The intended consequences of the malicious HTTP requests will be observed in the HTTP infrastructure response to the normal/benign HTTP request to confirm applicability of identified vulnerabilities in the adversary's plan of attack.

Techniques
Continue the monitoring of HTTP traffic.
Utilize different sequences of special characters (CR - Carriage Return, LF - Line Feed, HT - Horizontal Tab, SP - Space and etc.) to bypass filtering and back-end encoding and to embed: additional HTTP Requests with their own headers malicious web scripts into parameters of HTTP Request headers (e.g., browser cookies like Set-Cookie or Ajax web/browser object parameters like XMLHttpRequest) adversary chosen encoding (e.g., UTF-7) to utilize additional special characters (e.g., > and <) filtered by the target HTTP agent. Note that certain special characters and character encoding may be applicable only to intermediary and front-end agents with rare configurations or that are not RFC compliant.
Follow an unrecognized (sometimes a RFC compliant) HTTP header with a subsequent HTTP request to potentially cause the HTTP request to be ignored and interpreted as part of the preceding HTTP request.

Perform HTTP Request Splitting attack: Using knowledge discovered in the experiment section above, smuggle a message to cause one of the consequences.

Techniques
Leverage techniques identified in the Experiment Phase.

HTTP Request Splitting