A better zip bomb


David Fifield

Awarded Best Paper!


We show how to construct a non-recursive zip bomb that achieves a high compression ratio by overlapping files inside the zip container. "Non-recursive" means that it does not rely on a decompressor's recursively unpacking zip files nested within zip files: it expands fully after a single round of decompression. The output size increases quadratically in the input size, reaching a compression ratio of over 28 million (10 MB → 281 TB) at the limits of the zip format. Even greater expansion is possible using 64-bit extensions. The construction uses only the most common compression algorithm, DEFLATE, and is compatible with most zip parsers.

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@inproceedings {238588,
author = {David Fifield},
title = {A better zip bomb},
booktitle = {13th USENIX Workshop on Offensive Technologies (WOOT 19)},
year = {2019},
address = {Santa Clara, CA},
url = {https://www.usenix.org/conference/woot19/presentation/fifield},
publisher = {USENIX Association},
month = aug,