Permissions, Privileges, and Access Controls
Spring Framework, versions 5.0 prior to 5.0.5 and versions 4.3 prior to 4.3.15 and older unsupported versions, provide client-side support for multipart requests. When Spring MVC or Spring WebFlux server application (server A) receives input from a remote client, and then uses that input to make a multipart request to another server (server B), it can be exposed to an attack, where an extra multipart is inserted in the content of the request from server A, causing server B to use the wrong value for a part it expects. This could to lead privilege escalation, for example, if the part content represents a username or user roles.
CWE-264 - Permissions Privileges and Access Controls
CWE 264 (permissions, privileges, and access controls) is not a weakness in and of itself, rather it is a category of weaknesses related to the management of permissions, privileges, and other security features used to perform access control. If not addressed, the weaknesses in this category allow attackers to gain privileges for an unintended sphere of control, access sensitive information, and execute arbitrary commands.