Insecure Deserialization

Introduction

We have discussed in the previous post regarding the introduction, basically Insecure deserialization is a critical vulnerability that often lurks in legacy systems and internal applications. Serialization and deserialization are foundational operations in modern software development, enabling communication between systems, data storage, and object persistence. However, improper use of deserialization—particularly with unsafe serializers like .NET’s BinaryFormatter—can open the door to severe vulnerabilities, including remote code execution (RCE).

This blog post will unpack the risks associated with insecure deserialization, illustrate real-world vulnerable patterns, and explore multiple remediation strategies. We’ll focus especially on the dangers of the legacy BinaryFormatter class and how developers can safely move away from it.

In the realm of cybersecurity, one vulnerability that continues to haunt developers and security professionals alike is insecure deserialization. This seemingly innocuous process, crucial for transferring data between systems, harbors a myriad of risks when implemented carelessly. We delve deep into the intricacies of insecure deserialization, uncover its potential threats. I will also demonstrate practical examples in PHP, Java, and Python.

What is serialization

Serialization is the process of converting complex data structures, such as objects and their fields, into a “flatter” format that can be sent and received as a sequential stream of bytes. Serializing data makes it much simpler to:

• Write complex data to inter-process memory, a file, or a database
• Send complex data, for example, over a network, between different components of an application, or in an API call

Crucially, when serializing an object, its state is also persisted. In other words, the object’s attributes are preserved, along with their assigned values.