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README.md

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+---
+license: apache-2.0
+tags:
+  - security
+  - proof-of-concept
+  - avro
+  - denial-of-service
+  - model-format-vulnerability
+---
+
+# Avro huge declared metadata length memory DoS PoC
+
+Benign security PoC for a Model Format Vulnerability report.
+
+The malicious Avro object-container file is 158 bytes. It is generated from a valid control Avro file, then the encoded byte length of the `avro.schema` metadata value is changed to `2147483647`.
+
+When loaded, both latest Python Avro readers tested allocate/read based on the attacker-controlled declared length before validating that the tiny file contains that many bytes:
+
+- `fastavro==1.12.2`
+- `avro==1.12.1`
+
+The reproducer runs each loader in a child process with a 512 MB address-space limit so the host is not exhausted.
+
+## Files
+
+- `control.avro` - valid 155-byte Avro object-container file.
+- `malicious-huge-avro-schema-length.avro` - 158-byte mutated file.
+- `reproduce.py` - self-contained generator and loader reproducer.
+- `reproduce-result.json` - local run output.
+- `picklescan-malicious.txt` - picklescan output.
+- `modelscan-malicious.txt` - modelscan output.
+- `SHA256SUMS.txt` - artifact hashes.
+
+## Reproduce
+
+```bash
+python3 -m venv /tmp/avro-mfvpoc
+/tmp/avro-mfvpoc/bin/python -m pip install --upgrade pip fastavro==1.12.2 avro==1.12.1
+/tmp/avro-mfvpoc/bin/python reproduce.py
+```
+
+Expected result:
+
+```text
+control.avro + fastavro: loads successfully
+control.avro + apache-avro: loads successfully
+malicious-huge-avro-schema-length.avro + fastavro: MemoryError
+malicious-huge-avro-schema-length.avro + apache-avro: MemoryError
+```
+
+The PoC does not execute code and does not write outside its temporary working directory.