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gh-157190: Follow symlinks when extracting tarfile hard links #157191

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gh-157190: Follow symlinks when extracting tarfile hard links #157191

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480ea4a
Fix symlink escape via `tarfile` hard link to symlink
StanFromIreland Sep 6, 2026
ac398e3
Drop news entry for this branch.
StanFromIreland Sep 8, 2026
027cfba
`skip_unless_hardlink` for Android/Emscriptem.
StanFromIreland Sep 8, 2026
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6 changes: 5 additions & 1 deletion Lib/tarfile.py
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Original file line number Diff line number Diff line change
Expand Up @@ -2813,7 +2813,11 @@ def makelink_with_filter(self, tarinfo, targetpath,
if os.path.lexists(targetpath):
# Avoid FileExistsError on following os.link.
os.unlink(targetpath)
os.link(tarinfo._link_target, targetpath)
# Resolve the target so the hard link points to the file
# itself. Otherwise os.link() may duplicate a symlink to a
# shallower location, where it's relative target escapes the
# destination directory. (CVE-2026-82049)
os.link(os.path.realpath(tarinfo._link_target), targetpath)
return
except symlink_exception:
keyerror_to_extracterror = True
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18 changes: 18 additions & 0 deletions Lib/test/test_tarfile.py
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Expand Up @@ -4642,6 +4642,24 @@ def test_sneaky_hardlink_fallback_deep(self):
self.expect_file("a/b/s", symlink_to=os.path.join('..', 'escape'))
self.expect_file("s", symlink_to=os.path.join('..', 'escape'))

@symlink_test
@os_helper.skip_unless_hardlink
def test_sneaky_hardlink_relocation(self):
with ArchiveMaker() as arc:
arc.add("a/escape", content="decoy")
arc.add("a/b/s", symlink_to=os.path.join("..", "escape"))
arc.add("s", hardlink_to=os.path.join("a", "b", "s"))

for filter in 'data', 'tar':
with self.subTest(filter), self.check_context(arc.open(), filter):
self.expect_file("a/escape", content="decoy")
if os_helper.can_symlink():
self.expect_file("a/b/s", symlink_to=os.path.join('..', 'escape'))
else:
self.expect_file("a/b/s", content="decoy")
self.expect_file("s", content="decoy")
self.assertFalse((self.destdir / "s").is_symlink())

@symlink_test
def test_exfiltration_via_symlink(self):
# (CVE-2025-4138)
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