python3: fix CVE-2026-11972

When using the "tarfile" module with a file opened in "streaming mode"
(mode="r|") the tarfile module did not properly handle EOF, making archive
parsing take exponentially longer.

(From OE-Core rev: 9c066bcd634e7b938a10c64ef1eaf322a99ec434)

Signed-off-by: Benjamin Robin (Schneider Electric) <benjamin.robin@bootlin.com>
Signed-off-by: Mathieu Dubois-Briand <mathieu.dubois-briand@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
(cherry picked from commit bbd9c82298880ab61b9befea97dfe8a0a4943836)
Signed-off-by: Yoann Congal <yoann.congal@smile.fr>
Signed-off-by: Paul Barker <paul@pbarker.dev>

meta/recipes-devtools/python/python3/CVE-2026-11972.patch

@@ -0,0 +1,60 @@
+From a83ebdb495a9cbd28a03675acdeda235fade90b3 Mon Sep 17 00:00:00 2001
+From: Petr Viktorin <encukou@gmail.com>
+Date: Tue, 23 Jun 2026 15:13:30 +0200
+Subject: [PATCH] gh-151981: Make tarfile._Stream.seek break at EOF (GH-151982)
+
+Co-authored-by: Stan Ulbrych <stan@python.org>
+
+CVE: CVE-2026-11972
+Upstream-Status: Backport [https://github.com/python/cpython/commit/f50bf13566189c8d0ce5a814f33eff3d89951896]
+
+Signed-off-by: Benjamin Robin <benjamin.robin@bootlin.com>
+---
+ Lib/tarfile.py           |  4 +++-
+ Lib/test/test_tarfile.py | 16 ++++++++++++++++
+ 2 files changed, 19 insertions(+), 1 deletion(-)
+
+diff --git a/Lib/tarfile.py b/Lib/tarfile.py
+index 83226e907e4b..c0007a78f700 100755
+--- a/Lib/tarfile.py
++++ b/Lib/tarfile.py
+@@ -516,7 +516,9 @@ def seek(self, pos=0):
+         if pos - self.pos >= 0:
+             blocks, remainder = divmod(pos - self.pos, self.bufsize)
+             for i in range(blocks):
+-                self.read(self.bufsize)
++                data = self.read(self.bufsize)
++                if not data:
++                    break
+             self.read(remainder)
+         else:
+             raise StreamError("seeking backwards is not allowed")
+diff --git a/Lib/test/test_tarfile.py b/Lib/test/test_tarfile.py
+index 29719d95b6c1..8aeb2e1b1b9a 100644
+--- a/Lib/test/test_tarfile.py
++++ b/Lib/test/test_tarfile.py
+@@ -4480,6 +4480,22 @@ def valueerror_filter(tarinfo, path):
+         with self.check_context(arc.open(errorlevel='boo!'), filtererror_filter):
+             self.expect_exception(TypeError)  # errorlevel is not int
+
++    @support.subTests('format', [tarfile.GNU_FORMAT, tarfile.PAX_FORMAT])
++    def test_getmembers_big_size(self, format):
++        # gh-151981: A loop in seek() for streaming files tried to read the
++        # declared number of blocks even at EOF
++        tinfo = tarfile.TarInfo("huge-file")
++        tinfo.size = 1 << 64
++        bio = io.BytesIO()
++        # Write header without data
++        bio.write(tinfo.tobuf(format))
++
++        # Reset & try to get contents
++        bio.seek(0)
++        with tarfile.open(fileobj=bio, mode="r|") as tar:
++            with self.assertRaises(tarfile.ReadError):
++                tar.getmembers()
++
+
+ class OverwriteTests(archiver_tests.OverwriteTests, unittest.TestCase):
+     testdir = os.path.join(TEMPDIR, "testoverwrite")
+--
+2.54.0

meta/recipes-devtools/python/python3_3.12.13.bb

@@ -45,6 +45,7 @@ SRC_URI = "http://www.python.org/ftp/python/${PV}/Python-${PV}.tar.xz \
            file://CVE-2025-13462.patch \
            file://CVE-2026-4224.patch \
            file://CVE-2026-11940.patch \
+           file://CVE-2026-11972.patch \
            "
 
 SRC_URI:append:class-native = " \