# Java Insecure Deserialization (ObjectInputStream)

> Detects Java ObjectInputStream.readObject() on untrusted data, enabling remote code execution via gadget chains.

- Skill: `zakirkun/java-insecure-deserialization-objectinputstream` (Agent Skill, multi-file: 2 files)
- Install (CLI): `npx skillmds@latest add zakirkun/java-insecure-deserialization-objectinputstream`
- Raw SKILL.md: https://api.skillmd.com/api/skills/zakirkun/java-insecure-deserialization-objectinputstream/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: zakirkun (https://skillmd.com/u/zakirkun)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/zakirkun/java-insecure-deserialization-objectinputstream

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# Java Insecure Deserialization

## Overview
Java's `ObjectInputStream.readObject()` deserializes objects from byte streams. When called with untrusted data, attackers can use "gadget chains" from libraries like Commons Collections, Spring, and Apache to achieve Remote Code Execution.

Famous exploits: Apache Struts, Jenkins, WebLogic, JBoss all suffered RCE from this vulnerability.

## Remediation
- Replace Java serialization with JSON/XML with schema validation
- Use `ObjectInputFilter` (Java 9+) to restrict deserializable classes
- Use serialization filtering frameworks like SerialKiller