loowr/gguf-poc

GGUF Python Reader -- Missing Bounds Checks (DoS)

Summary

The Python GGUF reader in llama.cpp's gguf-py library lacks the input validation bounds that the C++ implementation has, allowing a maliciously crafted GGUF file to cause denial of service through excessive memory allocation or infinite looping.

The C++ parser caps string lengths and array counts at 1 GiB (GGUF_MAX_STRING_LENGTH, GGUF_MAX_ARRAY_ELEMENTS). The Python parser has no equivalent checks.

Affected code

• Repository: https://github.com/ggerganov/llama.cpp
• File: gguf-py/gguf/gguf_reader.py
• Commit tested: aa50b2c2ae91326d5aad956ceeb015d1d48e626b

PoC file

malicious_gguf.gguf -- a 44-byte file that declares 100 million key-value pairs in its header, causing the parser to iterate endlessly.

Reproduction

pip install gguf numpy
python reproduce.py

Expected: the script hangs indefinitely trying to parse a 44-byte file.

Impact

Any Python application using GGUFReader on untrusted GGUF files is affected. This includes CLI tools shipped with gguf-py and any application that loads GGUF models from user-supplied paths.

Fix

Add the bounds checks from the C++ implementation to the Python reader:

• Maximum string length
• Maximum array element count
• KV pair and tensor count validation before iteration