GeezerVison is showing github.com — gh-146581: Use ZipFile.extractall() in shutil for secure ZIP extraction by Shrey-N · Pull Request #146588 · python/cpython
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Shrey-N
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Mar 29, 2026
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edited by bedevere-app
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This PR refactors shutil._unpack_zipfile to use zipfile.ZipFile.extractall() instead of a manual extraction loop. This resolves a directory traversal vulnerability on Windows where archives containing drive prefixed paths for exampleD:/file.txt could write files outside the intended destination directory.
Changes Made
- Replaced manual path joining and validation with
ZipFile.extractall(), which leverages the zipfile module
- Updated the
_unpack_zipfile signature to accept **kwargs. This ensures compatibility with the filter argument, preventing TypeError while allowing future filter support for ZIP files.
- This change brings ZIP extraction in line with how
shutil handles TAR files, which already uses extractall().
Regression Test
Added a new test case test_unpack_zipfile_traversal_windows_drive to Lib/test/test_shutil.py. This test specifically verifies that a ZIP file containing a drive prefixed path is safely sanitized and extracted within the intended extract_dir on Windows.
Linked Issue
#146581
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Add a test case for ZIP file traversal on Windows.
Updated comments for clarity and removed redundant lines.
Removed unnecessary blank lines in _unpack_zipfile function.
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Thank you for your PR, @Shrey-N, but we already discussed this issue and created a solution. #146591 is in general similar to your PR, but includes results of that discussion.
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Reviewers
giampaolo
Awaiting requested review from giampaolo
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