Introduction
Modern applications constantly exchange structured data between systems. To make this possible, developers rely on a process called serialization, which converts objects into formats that applications can store or transmit. However, when this process is implemented without proper validation, it opens the door to insecure deserialization.
Insecure deserialization vulnerabilities allow attackers to manipulate serialized objects and inject malicious behaviour. As a result, applications may execute unintended actions, expose sensitive data, or even run attacker-controlled commands.
This risk has become more serious as frameworks, APIs, and client-side libraries grow more complex. Therefore, understanding how insecure deserialization works is essential for developers, security teams, and organisations building modern software.
What Is Insecure Deserialization?
Insecure deserialization occurs when an application accepts serialized data from an untrusted source and converts it back into objects without sufficient validation.
To understand this clearly, let’s break down the key terms:
- Serialization is the process of converting an object into a format like JSON, XML, or binary so it can be stored or transmitted.
- Deserialization is the reverse process, where that data is converted back into a live object.
- Object injection happens when attackers manipulate serialized data to influence how objects behave during deserialization.
When applications trust serialized input blindly, attackers can alter object properties or execution flow. In some cases, this manipulation results in remote code execution (RCE), where the attacker gains the ability to run commands on the server or client system.
Insecure deserialization is listed by OWASP as a critical application security risk because it often leads to severe impacts such as remote code execution. Read more about itby clicking here .
How Insecure Deserialization Attacks Work
Although the technical details vary across languages and frameworks, the attack flow usually follows a predictable pattern.
Step 1: Application accepts serialized input
The application receives serialized data through:
- HTTP requests
- Cookies or tokens
- API payloads
- Client-side state
Step 2: Attacker modifies the serialized object
Instead of sending legitimate data, the attacker injects crafted values. These values may:
- Trigger dangerous methods
- Change object behaviour
- Reference unexpected classes or functions
Step 3: Unsafe deserialization occurs
The application deserializes the data automatically, assuming it is safe.
Step 4: Malicious behaviour executes
During or after deserialization, the injected object triggers unintended actions. Depending on the context, this may lead to:
- File access
- Command execution
- Logic bypass
- Full remote code execution
Step 5: Impact escalates
Once attackers gain execution capability, they often move laterally or persist inside the system.
Why Insecure Deserialization Leads to Remote Code Execution
Insecure deserialization often results in RCE because of how object-oriented systems work.
Magic methods and constructors
Many programming languages automatically execute methods when objects are created or destroyed.
Implicit trust in object behaviour
Developers often assume objects behave as expected.
Chained execution paths
Attackers chain harmless-looking methods into dangerous execution flows.
Lack of input validation
Serialized data is rarely validated at a deep level.
Framework abstraction
Modern frameworks hide complexity, which also hides risk.
Real-World Example: React2Shell and Remote Code Execution
A recent example that highlights this risk is the React2Shell vulnerability.
React2Shell demonstrated how unsafe handling of serialized or dynamically evaluated data in frontend-driven architectures can lead to remote code execution. While React itself is not inherently insecure, the vulnerability emerged from how data and object behaviour were handled in certain integration patterns.
In affected scenarios:
- Serialized data crossed trust boundaries
- Unsafe evaluation or object handling occurred
- Attackers gained the ability to execute arbitrary commands
This incident reinforced an important lesson: modern frameworks do not eliminate insecure deserialization risks. Instead, poor handling of object state and dynamic execution can recreate the same vulnerability patterns seen in backend systems.
Why Insecure Deserialization Is Growing Now
Several trends explain why this vulnerability appears more frequently today.
Heavy use of APIs
APIs exchange structured objects constantly.
Client-side logic expansion
Frontend applications handle more state and logic than ever before.
Microservices architecture
Objects move across services with inconsistent validation.
Developer convenience features
Automatic serialization reduces manual checks.
Increased use of third-party libraries
Dependencies introduce hidden deserialization behaviour.
Why Insecure Deserialization Is Hard to Detect
Unlike injection attacks, insecure deserialization does not always look malicious.
Traffic appears normal
Serialized data looks legitimate.
No syntax errors
Payloads often follow valid formats.
Limited logging visibility
Deserialization happens deep inside application logic.
Delayed execution
Malicious behaviour may trigger later.
Framework abstraction
Security tools may not inspect object behaviour.
Impact on Businesses / Individuals
For Businesses
- Remote code execution risk
- Data breaches and leaks
- Service disruption
- Regulatory penalties
- Loss of customer trust
- Increased incident response costs
For Individuals
- Exposure of personal data
- Account compromise
- Malware infections
- Identity theft
- Loss of privacy
How to Prevent Insecure Deserialization
Preventing insecure deserialization requires disciplined design.
Avoid deserializing untrusted data
Treat external input as hostile.
Use safe data formats
Prefer simple formats without executable behaviour.
Implement strict validation
Validate structure and content before deserialization.
Disable dangerous object features
Avoid automatic method execution.
Apply least privilege principles
Limit what deserialized objects can do.
Monitor application behaviour
Unexpected execution paths should raise alerts.
Educate development teams
Understanding object behaviour reduces mistakes.
Conclusion
Insecure deserialization vulnerabilities demonstrate how dangerous blind trust in object handling can be. By manipulating serialized data, attackers can trigger object injection and, in severe cases, achieve remote code execution.
The React2Shell example shows that this risk extends beyond traditional backend systems and into modern frontend architectures. Therefore, organisations must treat serialization and deserialization as critical security boundaries.
At eSHIELD IT Services, we help businesses identify and mitigate complex vulnerabilities like insecure deserialization through secure design practices and real-world threat modelling. Ultimately, secure software depends not on convenience, but on careful control of how data becomes code.
FAQ
What is insecure deserialization?
It happens when untrusted serialized data is converted into objects without validation.
Why is insecure deserialization dangerous?
It can lead to remote code execution or data breaches.
Does insecure deserialization only affect backend systems?
No, frontend and API systems can also be affected.
How does object injection work?
Attackers manipulate object properties to trigger unintended behaviour.
Can insecure deserialization cause RCE?
Yes, it is a common path to remote code execution.
Is JSON safe from deserialization attacks?
Only if properly validated and handled.
Are modern frameworks immune?
No, misuse can recreate the vulnerability.
How do attackers find these flaws?
They test serialized inputs for unexpected behaviour.
Is this vulnerability easy to exploit?
It depends on application design and protections.
Who should fix insecure deserialization issues?
Developers and security teams must work together.
