gh-161323: Refuse drive-relative paths in tarfile extraction filters

Doc/library/tarfile.rst

@@ -1120,14 +1120,15 @@ reused in custom filters:
   Implements the ``'tar'`` filter.
 
   - Strip leading slashes (``/`` and :data:`os.sep`) from filenames.
-  - :ref:`Refuse <tarfile-extraction-refuse>` to extract files with absolute
-    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 with absolute
+    paths (in case the name is absolute
+    even after stripping slashes, e.g. ``C:/foo`` on Windows)
+    or with a drive (e.g. ``C:foo`` on Windows).
+    This raises :class:`~tarfile.AbsolutePathError`.
   - :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`.
@@ -1152,6 +1153,10 @@ reused in custom filters:
 
      Filenames containing ``..`` components are now normalized.
 
+  .. versionchanged:: next
+
+     Filenames with a drive that are not absolute are now refused.
+
 .. function:: data_filter(member, path)
 
   Implements the ``'data'`` filter.
@@ -1164,7 +1169,8 @@ reused in custom filters:
     symbolic links.
 
   - :ref:`Refuse <tarfile-extraction-refuse>` to extract links (hard or soft)
-    that link to absolute paths, or ones that link outside the destination.
+    that link to absolute paths or to paths with a drive,
+    or ones that link outside the destination.
 
     This raises :class:`~tarfile.AbsoluteLinkError` or
     :class:`~tarfile.LinkOutsideDestinationError`.
@@ -1198,6 +1204,10 @@ reused in custom filters:
 
      Link targets are now normalized.
 
+  .. versionchanged:: next
+
+     Link targets with a drive that are not absolute are now refused.
+
 
 .. _tarfile-extraction-refuse:
 

Lib/tarfile.py

@@ -839,10 +839,6 @@ def _get_filtered_attrs(member, dest_path, for_data=True):
     # Include os.sep (target OS directory separator) as well.
     if name.startswith(('/', os.sep)):
         name = new_attrs['name'] = member.path.lstrip('/' + os.sep)
-    if os.path.isabs(name):
-        # Path is absolute even after stripping.
-        # 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
@@ -851,6 +847,11 @@ def _get_filtered_attrs(member, dest_path, for_data=True):
         normalized = os.path.normpath(name)
         if normalized != name:
             name = new_attrs['name'] = normalized
+    if os.path.isabs(name) or os.path.splitdrive(name)[0]:
+        # Path is absolute even after stripping, or has a drive.
+        # For example, 'C:/foo' or 'C:foo' on Windows.
+        # os.path.join() ignores a destination without a drive for 'C:foo'.
+        raise AbsolutePathError(member)
     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:
@@ -894,11 +895,11 @@ def _get_filtered_attrs(member, dest_path, for_data=True):
             new_attrs['gname'] = None
         # Check link destination for 'data'
         if member.islnk() or member.issym():
-            if os.path.isabs(member.linkname):
-                raise AbsoluteLinkError(member)
             normalized = os.path.normpath(member.linkname)
             if normalized != member.linkname:
                 new_attrs['linkname'] = normalized
+            if os.path.isabs(normalized) or os.path.splitdrive(normalized)[0]:
+                raise AbsoluteLinkError(member)
             if member.issym():
                 # The symlink is created at `name` with trailing separators
                 # stripped, so its target is relative to the directory

Lib/test/test_tarfile.py

@@ -3,6 +3,7 @@
 import sys
 import os
 import io
+import ntpath
 from hashlib import sha256
 from contextlib import contextmanager, ExitStack
 from random import Random
@@ -4298,6 +4299,47 @@ def test_absolute(self):
                         tarfile.AbsolutePathError,
                         """['"].*escaped.evil['"] has an absolute path""")
 
+    def test_drive_relative(self):
+        # Test names and link targets that have a drive but no root.
+        # They are not absolute, but os.path.join() does not put them
+        # below a destination that has no drive or another drive.
+        # Windows path handling is used on all platforms.
+        dest = r'C:\outerdir\dest'
+        with support.swap_attr(os, 'path', ntpath):
+            for name in 'C:escaped.evil', 'x/../C:escaped.evil':
+                for filter in tarfile.tar_filter, tarfile.data_filter:
+                    with self.subTest(name=name, filter=filter.__name__):
+                        with self.assertRaises(tarfile.AbsolutePathError):
+                            filter(tarfile.TarInfo(name), dest)
+
+            for linkname in 'C:escaped.evil', 'x/../C:escaped.evil', './C:evil':
+                for type in tarfile.SYMTYPE, tarfile.LNKTYPE:
+                    with self.subTest(linkname=linkname, type=type):
+                        member = tarfile.TarInfo('link')
+                        member.type = type
+                        member.linkname = linkname
+                        with self.assertRaises(tarfile.AbsoluteLinkError):
+                            tarfile.data_filter(member, dest)
+
+            member = tarfile.TarInfo('x/../C/benign.txt')
+            member = tarfile.data_filter(member, dest)
+            self.assertEqual(member.name, r'C\benign.txt')
+
+    @unittest.skipUnless(os.name == 'nt', 'requires Windows drives')
+    def test_drive_relative_to_cwd(self):
+        # Test a name like 'C:escaped.evil' with a destination that has no
+        # drive. The file must not be created in the current directory.
+        with os_helper.temp_cwd() as cwd:
+            drive = os.path.splitdrive(cwd)[0]
+            with ArchiveMaker() as arc:
+                arc.add(f'{drive}escaped.evil')
+
+            for filter in 'tar', 'data':
+                with self.subTest(filter=filter), arc.open() as tar:
+                    with self.assertRaises(tarfile.AbsolutePathError):
+                        tar.extractall('dest', filter=filter)
+                    self.assertFalse(os.path.lexists('escaped.evil'))
+
     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

Misc/NEWS.d/next/Security/2026-10-22-08-07-52.gh-issue-161323.q7Drv2.rst

@@ -0,0 +1,5 @@
+On Windows, the ``'tar'`` and ``'data'`` :mod:`tarfile` extraction filters
+now refuse member names and link targets that have a drive but are not
+absolute, such as ``C:foo``, with :exc:`~tarfile.AbsolutePathError` or
+:exc:`~tarfile.AbsoluteLinkError`. Such members could be extracted outside
+the destination directory.  Fixes :cve:`2026-107784`.