# DL4J Arbitrary Class Instantiation Vulnerability PoC

## Vulnerability Summary

**Type:** Arbitrary Class Instantiation via Unvalidated Model Configuration  
**Severity:** Critical (Remote Code Execution)  
**Affected Component:** `org.deeplearning4j.models.embeddings.loader.WordVectorSerializer`  

## Vulnerable Code

File: `deeplearning4j/deeplearning4j-nlp-parent/deeplearning4j-nlp/src/main/java/org/deeplearning4j/models/embeddings/loader/WordVectorSerializer.java`
Lines: 3067-3069

```java
String tokenizerFactoryClassName = configuration.getTokenizerFactory();
TokenizerFactory factory = DL4JClassLoading.createNewInstance(tokenizerFactoryClassName);
```

## Attack Vector

Attacker creates a malicious Word2Vec model (.zip) with tokenizerFactory pointing to arbitrary Java classes like java.lang.ProcessBuilder.

## Impact

- Remote Code Execution (RCE)
- Arbitrary Class Instantiation  
- Denial of Service

## Remediation

Implement class allowlist for tokenizer factory classes.