From 78b65b9d5a36e63becb3394b104c5508aba9eefa Mon Sep 17 00:00:00 2001
From: Stan Ulbrych <stan@python.org>
Date: Thu, 22 Oct 2026 21:23:08 +0100
Subject: [PATCH] gh-160097: Reject links replacing the destination in
 `tarfile.tar_filter` (GH-160098) (cherry picked from commit
 e7e0b3523ad6ba8472873dda594cf4021a16f8b5)

Co-authored-by: Stan Ulbrych <stan@python.org>
---
 Doc/library/tarfile.rst                               |  5 +++++
 Lib/tarfile.py                                        | 11 ++++++-----
 Lib/test/test_tarfile.py                              |  6 ++++--
 .../2026-10-21-19-58-53.gh-issue-160097.-opfAL.rst    |  5 +++++
 4 files changed, 20 insertions(+), 7 deletions(-)
 create mode 100644 Misc/NEWS.d/next/Security/2026-10-21-19-58-53.gh-issue-160097.-opfAL.rst

diff --git a/Doc/library/tarfile.rst b/Doc/library/tarfile.rst
index e8c272cb39716b..27bf353fe76bca 100644
--- a/Doc/library/tarfile.rst
+++ b/Doc/library/tarfile.rst
@@ -1040,6 +1040,11 @@ reused in custom filters:
   - :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`.
+  - :ref:`Refuse <tarfile-extraction-refuse>` to extract links (hard or soft)
+    whose name refers to the destination directory itself.
+    This raises :class:`~tarfile.OutsideDestinationError`.
+    Note that such files are refused even on platforms that do not support
+    symbolic links.
   - Clear high mode bits (setuid, setgid, sticky) and group/other write bits
     (:const:`~stat.S_IWGRP` | :const:`~stat.S_IWOTH`).
 
diff --git a/Lib/tarfile.py b/Lib/tarfile.py
index 8c2dd869db4788..a35773017e5cb7 100755
--- a/Lib/tarfile.py
+++ b/Lib/tarfile.py
@@ -789,6 +789,12 @@ def _get_filtered_attrs(member, dest_path, for_data=True):
                                    strict=os.path.ALLOW_MISSING)
     if os.path.commonpath([target_path, dest_path]) != dest_path:
         raise OutsideDestinationError(member, target_path)
+    # A link member named after the destination directory itself
+    # would replace it with a (sym)link, redirecting the destination
+    # for all subsequent members.
+    if ((member.islnk() or member.issym())
+            and os.path.normpath(name) == os.curdir):
+        raise OutsideDestinationError(member, target_path)
     # Limit permissions (no high bits, and go-w)
     mode = member.mode
     if mode is not None:
@@ -824,11 +830,6 @@ def _get_filtered_attrs(member, dest_path, for_data=True):
         if member.islnk() or member.issym():
             if os.path.isabs(member.linkname):
                 raise AbsoluteLinkError(member)
-            # A link member that resolves to the destination directory itself
-            # would replace it with a (sym)link, redirecting the destination
-            # for all subsequent members.
-            if target_path == dest_path:
-                raise OutsideDestinationError(member, target_path)
             normalized = os.path.normpath(member.linkname)
             if normalized != member.linkname:
                 new_attrs['linkname'] = normalized
diff --git a/Lib/test/test_tarfile.py b/Lib/test/test_tarfile.py
index c4009927b0aa3b..01747fcf6e16fb 100644
--- a/Lib/test/test_tarfile.py
+++ b/Lib/test/test_tarfile.py
@@ -3971,8 +3971,10 @@ def test_link_at_destination(self):
                 t.linkname = '.'
                 arc.tar_w.addfile(t)
 
-            with self.check_context(arc.open(), 'data'):
-                self.expect_exception(tarfile.OutsideDestinationError)
+            for filter in 'tar', 'data':
+                with self.subTest(name=name, filter=filter):
+                    with self.check_context(arc.open(), filter):
+                        self.expect_exception(tarfile.OutsideDestinationError)
 
     @symlink_test
     @os_helper.skip_unless_symlink
diff --git a/Misc/NEWS.d/next/Security/2026-10-21-19-58-53.gh-issue-160097.-opfAL.rst b/Misc/NEWS.d/next/Security/2026-10-21-19-58-53.gh-issue-160097.-opfAL.rst
new file mode 100644
index 00000000000000..b48c8f7213ee82
--- /dev/null
+++ b/Misc/NEWS.d/next/Security/2026-10-21-19-58-53.gh-issue-160097.-opfAL.rst
@@ -0,0 +1,5 @@
+.. cve: CVE-2026-114583
+
+:func:`tarfile.tar_filter` now rejects link members whose path resolves to
+the destination directory itself, as :func:`tarfile.data_filter` already
+did.