agoo prior to 2.14.0 allows request smuggling attacks where agoo is used as a backend and a frontend proxy also being vulnerable. HTTP pipelining issues and request smuggling attacks might be possible due to incorrect Content-Length and Transfer encoding header parsing. It is possible to conduct HTTP request smuggling attacks where `agoo` is used as part of a chain of backend servers due to insufficient `Content-Length` and `Transfer Encoding` parsing.

Agoo before 2.14.3 does not reject GraphQL fragment spreads that form cycles, leading to an application crash. NOTE: the vendor has disputed this on the grounds that it is not the server's responsibility to "enforce all the various ways a developer could write code with logic errors.