An issue was discovered in Pivotal Spring Security 4.2.0.RELEASE through 4.2.2.RELEASE, and Spring Security 5.0.0.M1. When configured to enable default typing, Jackson contained a deserialization vulnerability that could lead to arbitrary code execution. Jackson fixed this vulnerability by blacklisting known deserialization gadgets. Spring Security configures Jackson with global default typing enabled, which means that (through the previous exploit) arbitrary code could be executed if all of the following is true: (1) Spring Securitys Jackson support is being leveraged by invoking SecurityJackson2Modules.getModules(ClassLoader) or SecurityJackson2Modules.enableDefaultTyping(ObjectMapper); (2) Jackson is used to deserialize data that is not trusted (Spring Security does not perform deserialization using Jackson, so this is an explicit choice of the user); and (3) there is an unknown (Jackson is not blacklisting it already) deserialization gadget that allows code execution present on the classpath. Jackson provides a blacklisting approach to protecting against this type of attack, but Spring Security should be proactive against blocking unknown deserialization gadgets when Spring Security enables default typing.
The product deserializes untrusted data without sufficiently verifying that the resulting data will be valid.
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Spring_security | Vmware | 4.2.0-release (including) | 4.2.0-release (including) |
| Spring_security | Vmware | 4.2.1-release (including) | 4.2.1-release (including) |
| Spring_security | Vmware | 4.2.2-release (including) | 4.2.2-release (including) |
| Spring_security | Vmware | 5.0.0-m1 (including) | 5.0.0-m1 (including) |
It is often convenient to serialize objects for communication or to save them for later use. However, deserialized data or code can often be modified without using the provided accessor functions if it does not use cryptography to protect itself. Furthermore, any cryptography would still be client-side security – which is a dangerous security assumption. Data that is untrusted can not be trusted to be well-formed. When developers place no restrictions on “gadget chains,” or series of instances and method invocations that can self-execute during the deserialization process (i.e., before the object is returned to the caller), it is sometimes possible for attackers to leverage them to perform unauthorized actions, like generating a shell.