https://github.com/python/cpython/commit/038a0915fdbb872f8064c37e67e527a8a7c... commit: 038a0915fdbb872f8064c37e67e527a8a7c5236c branch: 3.15 author: Miss Islington (bot) <31488909+miss-islington@users.noreply.github.com> committer: hugovk <1324225+hugovk@users.noreply.github.com> date: 2026-08-31T22:01:32+03:00 summary: [3.15] gh-155999: `tarfile`: handle a member that leaves the destination but comes back (GH-156000) (#156040) gh-155999: `tarfile`: handle a member that leaves the destination but comes back (GH-156000) (cherry picked from commit 97688346ada2df3e5b9c279348862c3d64ab0823) Co-authored-by: Stan Ulbrych <stan@python.org> files: A Misc/NEWS.d/next/Security/2026-08-13-13-08-11.gh-issue-155999.Xt4rWq.rst M Doc/library/tarfile.rst M Lib/tarfile.py M Lib/test/test_tarfile.py diff --git a/Doc/library/tarfile.rst b/Doc/library/tarfile.rst index 29a329fdfeab15..dbd5c418bc2e25 100644 --- a/Doc/library/tarfile.rst +++ b/Doc/library/tarfile.rst @@ -1107,6 +1107,10 @@ reused in custom filters: paths (in case the name is absolute even after stripping slashes, e.g. ``C:/foo`` on Windows). This raises :class:`~tarfile.AbsolutePathError`. + - Normalize filenames (:attr:`TarInfo.name`) that contain ``..`` components + using :func:`os.path.normpath`. + Note that this removes internal ``..`` components, which may change the + meaning of the name if it traverses symbolic links. - :ref:`Refuse <tarfile-extraction-refuse>` to extract files whose absolute path (after following symlinks) would end up outside the destination. This raises :class:`~tarfile.OutsideDestinationError`. @@ -1115,6 +1119,10 @@ reused in custom filters: Return the modified ``TarInfo`` member. + .. versionchanged:: next + + Filenames containing ``..`` components are now normalized. + .. function:: data_filter(member, path) Implements the ``'data'`` filter. diff --git a/Lib/tarfile.py b/Lib/tarfile.py index fe28ea68cfd132..59543072e6d271 100644 --- a/Lib/tarfile.py +++ b/Lib/tarfile.py @@ -833,6 +833,13 @@ def _get_filtered_attrs(member, dest_path, for_data=True): # For example, 'C:/foo' on Windows. raise AbsolutePathError(member) # Ensure we stay in the destination + if '..' in name.replace(os.sep, '/').split('/'): + # Directories are created from the name as given, so a name that + # leaves the destination part-way through would create them + # outside it even if the resolved path stays inside. + normalized = os.path.normpath(name) + if normalized != name: + name = new_attrs['name'] = normalized target_path = os.path.realpath(os.path.join(dest_path, name), strict=os.path.ALLOW_MISSING) if os.path.commonpath([target_path, dest_path]) != dest_path: diff --git a/Lib/test/test_tarfile.py b/Lib/test/test_tarfile.py index 2c6f0da7887f53..6945a9e735bd18 100644 --- a/Lib/test/test_tarfile.py +++ b/Lib/test/test_tarfile.py @@ -3968,6 +3968,20 @@ def test_absolute(self): tarfile.AbsolutePathError, """['"].*escaped.evil['"] has an absolute path""") + def test_parent_dir_out_and_back(self): + # Test a member that leaves the destination and comes back. + # The containment check looks at the resolved path, which stays + # inside, but the intermediate directories are created from the + # name as given, which does not. + with ArchiveMaker() as arc: + arc.add(f'../escaped.evil/../{self.destdir.name}/sub/file', + content='content') + + for filter in 'tar', 'data': + with self.subTest(filter): + with self.check_context(arc.open(), filter): + self.expect_file('sub/file', content='content') + @symlink_test def test_parent_symlink(self): # Test interplaying symlinks diff --git a/Misc/NEWS.d/next/Security/2026-08-13-13-08-11.gh-issue-155999.Xt4rWq.rst b/Misc/NEWS.d/next/Security/2026-08-13-13-08-11.gh-issue-155999.Xt4rWq.rst new file mode 100644 index 00000000000000..59b725e55bbffd --- /dev/null +++ b/Misc/NEWS.d/next/Security/2026-08-13-13-08-11.gh-issue-155999.Xt4rWq.rst @@ -0,0 +1,5 @@ +Fix the :mod:`tarfile` ``tar`` and ``data`` extraction filters creating +directories outside the destination for members whose name leaves the +destination and returns to it, such as ``../evil/../dest/sub/file``. The +containment check used the resolved path, but intermediate directories were +created from the name as given.