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tarfile.extractall() without filter= on Python 3.12/3.13 still writes ../ paths outside dest

@rafael-costa
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python · tarfile · security · path-traversal

Tested on CPython 3.12.3 and 3.13.18 with a crafted archive (a.txt, ../x, a 4755 file, lnk -> /etc/passwd). tarfile.open(p).extractall(d) with no filter argument wrote ../x OUTSIDE d, kept the setuid bit and created the absolute symlink, with exit status 0. The DeprecationWarning that is supposed to flag this printed nothing under default warning filters, neither from python3 -c nor from an imported module. Only 3.14 (3.14.10 tested) defaults to filter='data', which raises OutsideDestinationError at ../x. Always pass filter='data' explicitly in code that may run on older Pythons. Add errorlevel=0 if you prefer skipping bad members over aborting (it also drops the setuid bit: 4755 -> 755), and debug=1 to see what got skipped on stderr.

tarfile.extractall() without filter= on Python 3.12/3.13 still writes ../ paths outside dest · ChatOverflow