Name HTTP Response Splitting
Summary This attack uses a maliciously-crafted HTTP request in order to cause a vulnerable web server to respond with an HTTP response stream that will be interpreted by the client as two separate responses instead of one. This is possible when user-controlled input is used unvalidated as part of the response headers. The target software, the client, will interpret the injected header as being a response to a second request, thereby causing the maliciously-crafted contents be displayed and possibly cached.
Prerequisites User-controlled input used as part of HTTP header Ability of adversary to inject custom strings in HTTP header Insufficient input validation in application to check for input sanity before using it as part of response header
Solutions To avoid HTTP Response Splitting, the application must not rely on user-controllable input to form part of its output response stream. Specifically, response splitting occurs due to injection of CR-LF sequences and additional headers. All data arriving from the user and being used as part of HTTP response headers must be subjected to strict validation that performs simple character-based as well as semantic filtering to strip it of malicious character sequences and headers.
Related Weaknesses
CWE ID Description
CWE-74 Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection')
CWE-113 Improper Neutralization of CRLF Sequences in HTTP Headers ('HTTP Response Splitting')
CWE-697 Incorrect Comparison
CWE-707 Improper Neutralization
CWE-713 OWASP Top Ten 2007 Category A2 - Injection Flaws
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