Definition
Insecure deserialization is a vulnerability that occurs when untrusted data is deserialized by an application. Deserialization is the process of converting data from a serialized format into an object that a program can use. If an attacker can control the data being deserialized, they can inject malicious code or manipulate application logic. This can lead to serious security breaches, including remote code execution, denial of service, or privilege escalation. For instance, an attacker might send a crafted serialized object that, when deserialized, executes arbitrary commands on the server. This differs from insecure serialization, which is about how data is serialized, not how it's deserialized. This concept is frequently tested on security certifications like CompTIA Security+ and CySA+.