---
license: mit
language:
- en
base_model: microsoft/codebert-base
pipeline_tag: text-classification
tags:
- code
- solidity
- smart-contracts
- security
- vulnerability-detection
widget:
- text: "function withdraw(uint amount) public { msg.sender.call.value(amount)(\"\"); balances[msg.sender] -= amount; }"
  example_title: Reentrancy
- text: "function forward(address target, bytes data) public { target.delegatecall(data); }"
  example_title: Delegatecall
- text: "function play() public { if (block.timestamp % 2 == 0) { winner = msg.sender; } }"
  example_title: Timestamp
---

# CodeBERT — Solidity Vulnerability Classifier (4-class)

Fine-tuned [`microsoft/codebert-base`](https://huggingface.co/microsoft/codebert-base)
that classifies a Solidity snippet into one of four vulnerability types:
**Reentrancy**, **Integer Overflow**, **Timestamp Dependency**, or
**Dangerous Delegatecall**.

Reproduces the approach of Hossain, Altarawneh & Roberts, ["Leveraging LLMs and
ML for Smart Contract Vulnerability Detection"](https://arxiv.org/abs/2501.02229),
IEEE CCWC 2025, on a smaller public dataset.

**Code, training pipeline and full evaluation:** [github.com/Riicko-19/smart-contract-vuln-detector](https://github.com/Riicko-19/smart-contract-vuln-detector)
— including a 5-seed variance study, a label-contamination analysis, and an
adversarial out-of-distribution probe.

## Usage

```python
from transformers import pipeline

clf = pipeline("text-classification", model="AbijithwearsHUGGIES/codebert-smart-contract-vuln")
clf("function withdraw(uint a) public { msg.sender.call.value(a)(\"\"); balances[msg.sender] -= a; }")
# [{'label': 'Reentrancy', 'score': ...}]
```

## Results

This checkpoint, on the held-out 59-contract test split:

| Metric | Value |
|---|---|
| Accuracy | 0.881 |
| Macro F1 | 0.871 |
| Reentrancy F1 | 0.957 |
| Dangerous Delegatecall F1 | 1.000 |
| Timestamp Dependency F1 | 0.897 |
| Integer Overflow F1 | 0.632 |

**Read those with care.** The test split has only 59 contracts, so one flipped
prediction moves a per-class F1 by roughly 0.09. Measured across 5 seeds, this
architecture averages:

| Model | Accuracy | Macro F1 | Reentrancy | Overflow |
|---|---|---|---|---|
| CodeBERT | 0.868 ±0.037 | 0.858 ±0.054 | 0.926 ±0.048 | 0.624 ±0.170 |
| DistilBERT | 0.834 ±0.071 | 0.826 ±0.061 | 0.949 ±0.018 | 0.508 ±0.168 |

A paired per-seed comparison found **no statistically significant difference**
between CodeBERT and DistilBERT (accuracy p=0.41, macro-F1 p=0.47, Integer
Overflow p=0.38). This checkpoint is simply the best single artifact from that
sweep, not evidence that CodeBERT is the better architecture here.

## Training

- 12 epochs, class-weighted cross-entropy (the dataset is imbalanced)
- Best checkpoint selected on **validation macro-F1**, not `eval_loss` —
  selecting on loss lets the majority class dominate and yields 0.00 F1 on
  Integer Overflow, because the "best" checkpoint abandons the minority class
- Max sequence length 512 (no truncation occurs; longest contract is 248 tokens)

## Data

387 labelled contracts from the
[Messi-Q/Smart-Contract-Dataset](https://github.com/Messi-Q/Smart-Contract-Dataset)
"Resource 2" release — Timestamp Dependency 174, Integer Overflow 80,
Reentrancy 71, Dangerous Delegatecall 62. Split 270 train / 58 val / 59 test.

This is roughly a sixth the size of the paper's 2,217-contract IR-Fuzz split
(which is not publicly redistributable), so treat these numbers as directional
rather than a reproduction.

## Limitations

- **Integer Overflow is weak** (F1 ~0.62, ±0.17 across seeds), and the cause is
  the label, not the model. Across all 387 contracts, the other three classes
  have a near-perfect syntactic signature (Reentrancy 100% contain
  `.call.value(`, Timestamp 100% contain `block.timestamp`/`now`, Delegatecall
  89% contain `.delegatecall(`). Integer Overflow has none of its own: 39% of
  its contracts contain the reentrancy pattern and 55% contain timestamp calls.
  The source dataset ships four *independent binary* labelled sets, and forcing
  a single label onto contracts that exhibit several vulnerabilities pushes the
  ambiguity into this class. Treating the task as multi-label would be the
  principled fix.
- **Forced-choice, not detection.** The model always returns one of four
  classes. It cannot say "no vulnerability", and it was trained only on
  vulnerable contracts. An out-of-distribution probe makes the cost concrete: a
  *pure math library* with no state, no external calls and no timestamps is
  classified Timestamp Dependency at **99.1%** confidence, and Python source
  code scores Integer Overflow at 93.7%. Confidence does not help — on benign
  inputs it reaches 99.1%, while genuine vulnerabilities go as low as 97.9%, so
  the ranges overlap and no threshold separates them. Never use this to decide
  whether a contract is safe.
- **It does generalise on genuinely vulnerable code**, which is the flip side:
  it correctly flags reentrancy written with modern `.call{value:}` syntax, and
  even reentrancy expressed through a callback with no low-level call at all —
  so it is not merely keyword matching.
- **Not a substitute for an audit.** This is a research/portfolio artifact
  trained on 387 contracts, not a security tool.

## License

MIT