Deserializing compromised object with MongoDB .NET/C# Driver may cause remote code execution

Vulnerability Description

Under very specific circumstances (see Required configuration section below), a privileged user is able to cause arbitrary code to be executed which may cause further disruption to services. This is specific to applications written in C#. This affects all MongoDB .NET/C# Driver versions prior to and including v2.18.0 Following configuration must be true for the vulnerability to be applicable: * Application must written in C# taking arbitrary data from users and serializing data using _t without any validation AND * Application must be running on a Windows host using the full .NET Framework, not .NET Core AND * Application must have domain model class with a property/field explicitly of type System.Object or a collection of type System.Object (against MongoDB best practice) AND * Malicious attacker must have unrestricted insert access to target database to add a _t discriminator."Following configuration must be true for the vulnerability to be applicable

References

• https://jira.mongodb.org/browse/CSHARP-4475
• https://github.com/mongodb/mongo-csharp-driver/releases/tag/v2.19.0