Microsoft IIS 5.0 and 6.0 allows remote attackers to poison the web cache, bypass web application firewall protection, and conduct XSS attacks via an HTTP request with both a "Transfer-Encoding: chunked" header and a Content-Length header, which causes IIS to incorrectly handle and forward the body of the request in a way that causes the receiving server to process it as a separate HTTP request, aka "HTTP Request Smuggling."

References

• https://nvd.nist.gov/vuln/detail/CVE-2005-2089
• https://exchange.xforce.ibmcloud.com/vulnerabilities/42899
• http://seclists.org/lists/bugtraq/2005/Jun/0025.html
• http://www.securiteam.com/securityreviews/5GP0220G0U.html
• http://www.watchfire.com/resources/HTTP-Request-Smuggling.pdf