SuperMartijn642s Config Lib is a library used by a number of mods for the game Minecraft. The versions of SuperMartijn642s Config Lib between 1.0.4 and 1.0.8 are affected by a vulnerability and can be exploited on both servers and clients. Using SuperMartijn642s Config Lib, servers will send a packet to clients with the servers config values. In order to read enum values from the packet data, ObjectInputStream#readObject is used. ObjectInputStream#readObject will instantiate a class based on the input data. Since, the packet data is not validated before ObjectInputStream#readObject is called, an attacker can instantiate any class by sending a malicious packet. If a suitable class is found, the vulnerability can lead to a number of exploits, including remote code execution. Although the vulnerable packet is typically only send from server to client, it can theoretically also be send from client to server. This means both clients and servers running SuperMartijn642s Config Lib between 1.0.4 and 1.0.8 are vulnerable. The vulnerability has been patched in SuperMartijn642s Config lib 1.0.9. Both, players and server owners, should update to 1.0.9 or higher.
The product deserializes untrusted data without sufficiently verifying that the resulting data will be valid.
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Config_lib | Config_lib_project | 1.0.4 (including) | 1.0.9 (excluding) |
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.