In Eclipse Jetty, versions 9.2.x and older, 9.3.x (all configurations), and 9.4.x (non-default configuration with RFC2616 compliance enabled), HTTP/0.9 is handled poorly. An HTTP/1 style request line (i.e. method space URI space version) that declares a version of HTTP/0.9 was accepted and treated as a 0.9 request. If deployed behind an intermediary that also accepted and passed through the 0.9 version (but did not act on it), then the response sent could be interpreted by the intermediary as HTTP/1 headers. This could be used to poison the cache if the server allowed the origin client to generate arbitrary content in the response.

In Eclipse Jetty versions 9.4.0 through 9.4.8, when using the optional Jetty provided FileSessionDataStore for persistent storage of HttpSession details, it is possible for a malicious user to access/hijack other HttpSessions and even delete unmatched HttpSessions present in the FileSystem's storage for the FileSessionDataStore.