Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')
Silverstripe before 3.7.5, 4.x before 4.4.7, 4.5.x before 4.5.4 and 4.6.0-beta1 through 4.6.0-rc1 which have opted into HTTP Cache Headers on responses served by the framework's HTTP layer can be vulnerable to web cache poisoning. Through modifying the X-Original-Url and X-HTTP-Method-Override headers, responses with malicious HTTP headers can return unexpected responses to other consumers of this cached response. Most other headers associated with web cache poisoning are already disabled through request hostname forgery whitelists.
CWE-444 - HTTP Request Smuggling
Entities such as web servers, web caching proxies, and application firewalls could parse HTTP requests differently. When there are two or more such entities in the path of an HTTP request, an attacker can send a specially crafted HTTP request that is seen as two different sets of requests by the attacked devices, allowing the attacker to smuggle a request into one device without the other device being aware of it. Such a vulnerability can prove devastating, for it enables further attacks on the application, like web cache poisoning, session hijacking, cross-site scripting, security bypassing, and sensitive information exposure.