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exploiting-deserialization

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Identify and exploit insecure deserialization across Java, .NET, PHP, Python, and Ruby — recognizing serialized formats by magic bytes, finding gadget chains with ysoserial and ysoserial.net, and detecting blind cases via DNS or timing. Use when a request contains base64 starting with rO0AB or AAEAAAD, when a cookie or parameter holds a serialized object, or when reviewing readObject, unserialize, pickle.loads, or Marshal.load.

secskills-offense/skills/exploiting-deserialization/SKILL.md

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Sep 4, 2026
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# Exploiting Deserialization

Deserialization turns attacker-controlled bytes into live objects with
attacker-chosen types. The vulnerability is not the parsing — it is that
constructing those objects runs code paths the developer never intended. The
work is recognizing the format, then finding a gadget chain in the libraries
that happen to be on the classpath.

Only against systems you are authorized to test.

## When to Use

- A cookie, parameter, header, or message body contains a serialized object
- You see the magic values listed below in traffic or storage
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