microsoft / microsoft/markitdown
[Security] Potential Denial of Service (DoS) via Zip Bomb in ZipConverter
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- Dominant language
- Python
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- Avg merge
- 1d 4h
- Merged PRs (30d)
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Description
A vulnerability was identified in the ZipConverter where it attempts to read the entire content of each file within a ZIP archive into memory simultaneously. This can be exploited using a "Zip Bomb" (a small ZIP file that decompresses to a very large size), leading to excessive memory consumption and potential system crashes (Out-of-Memory).‘
In packages/markitdown/src/markitdown/converters/_zip_converter.py, the code uses zipObj.read(name) to extract file contents:z_file_stream = io.BytesIO(zipObj.read(name))
Suggested Mitigation:
Check the file_size in ZipInfo before reading, and implement a configurable maximum size limit (e.g., 100MB). Alternatively, use a streaming approach if the underlying sub-converters support it.
Contributor guide
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First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start in packages/markitdown/src/markitdown/converters/_zip_converter.py and inspect how ZipInfo and zipObj.read(name) are used. Define and implement a bounded extraction behavior, then verify that ZIP entries exceeding the configured limit cannot cause unbounded memory use; the issue does not name a specific test file.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- python
- Domain
- security
- Issue type
- Bug
- Difficulty
- 3/5
- Estimated time
- 1-2 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 48/100