---
tags:
  - security
  - proof-of-concept
  - protobuf
license: mit
---

# Protocol Buffers DescriptorProto field materialization DoS PoC

This repository contains a benign security research PoC for a `.pb` artifact
that drives repeated-message materialization during
`descriptor_pb2.DescriptorProto.ParseFromString(...)`.

Files:

- `control_zero_field.pb`
- `malicious_field_5000000.pb`
- `reproduce.py`

Observed behavior:

- control artifact:
  - parses successfully with zero `field` entries
- malicious artifact:
  - parses successfully with `5,000,000` `field` entries
  - materially increases peak RSS during normal parse

Tested runtime:

```bash
python3 -m pip install protobuf==7.35.1
```

Public reproduction:

```bash
curl -L -O https://huggingface.co/hacnho/protobuf-descriptor-field-dos-poc/resolve/main/control_zero_field.pb
curl -L -O https://huggingface.co/hacnho/protobuf-descriptor-field-dos-poc/resolve/main/malicious_field_5000000.pb
curl -L -O https://huggingface.co/hacnho/protobuf-descriptor-field-dos-poc/resolve/main/reproduce.py
python3 reproduce.py --control control_zero_field.pb --malicious malicious_field_5000000.pb
```

Public files:

- `https://huggingface.co/hacnho/protobuf-descriptor-field-dos-poc/resolve/main/control_zero_field.pb`
- `https://huggingface.co/hacnho/protobuf-descriptor-field-dos-poc/resolve/main/malicious_field_5000000.pb`
- `https://huggingface.co/hacnho/protobuf-descriptor-field-dos-poc/resolve/main/reproduce.py`