Dec 28, 2025 · Dec 28, 2025 · Dec 28, 2025 · Dec 28, 2025 · Dec 28, 2025 · Dec 28, 2025
diff --git a/Doc/library/zoneinfo.rst b/Doc/library/zoneinfo.rst

    Objects created via this constructor cannot be pickled (see `pickling`_).

 :exc:`ValueError` is raised if the data read from *file_obj* is not a valid
    TZif file.

 ..classmethod::ZoneInfo.no_cache(key)

    An alternate constructor that bypasses the constructor's cache. It is
diff --git a/Lib/test/test_zoneinfo/test_zoneinfo.py b/Lib/test/test_zoneinfo/test_zoneinfo.py
        bad_zones = [
            b"",  # Empty file
            b"AAAA3" + b" " * 15,  # Bad magic
            # Truncated V2 file (should not loop indefinitely)
            b"TZif2" + (b"\x00" * 39) + b"TZif2" + (b"\x00" * 39) + b"\n" + b"Part",
        ]

        for bad_zone in bad_zones:
diff --git a/Lib/zoneinfo/_common.py b/Lib/zoneinfo/_common.py
        c = fobj.read(1)  # Should be \n
        assert c == b"\n", c

        tz_bytes = b""
        while (c := fobj.read(1)) != b"\n":
            tz_bytes += c

        tz_str = tz_bytes
        line = fobj.readline()
        if not line.endswith(b"\n"):
            raise ValueError("Invalid TZif file: unexpected end of file")
        tz_str = line.rstrip(b"\n")
    else:
        tz_str = None

diff --git a/Misc/NEWS.d/next/Library/2025-12-28-13-49-06.gh-issue-143241.5H4b8d.rst b/Misc/NEWS.d/next/Library/2025-12-28-13-49-06.gh-issue-143241.5H4b8d.rst
 :mod:`zoneinfo`: fix infinite loop in :meth:`ZoneInfo.from_file
 <zoneinfo.ZoneInfo.from_file>` when parsing a malformed TZif file. Patch by Fatih Celik.
Original file line number	Diff line number	Diff line change
Expand Up		@@ -206,6 +206,9 @@ The ``ZoneInfo`` class has two alternate constructors:

		Objects created via this constructor cannot be pickled (see `pickling`_).

		:exc:`ValueError` is raised if the data read from file_obj is not a valid
		TZif file.

		..classmethod::ZoneInfo.no_cache(key)

		An alternate constructor that bypasses the constructor's cache. It is
Expand Down
Original file line number	Diff line number	Diff line change
Expand Up		@@ -252,6 +252,8 @@ def test_bad_zones(self):
		bad_zones = [
		b"", # Empty file
		b"AAAA3" + b" " * 15, # Bad magic
		# Truncated V2 file (should not loop indefinitely)
		b"TZif2" + (b"\x00" * 39) + b"TZif2" + (b"\x00" * 39) + b"\n" + b"Part",
		]

		for bad_zone in bad_zones:
Expand Down
Original file line number	Diff line number	Diff line change
Expand Up		@@ -118,11 +118,10 @@ def get_abbr(idx):
		c = fobj.read(1) # Should be \n
		assert c == b"\n", c

		tz_bytes = b""
		while (c := fobj.read(1)) != b"\n":
		tz_bytes += c

		tz_str = tz_bytes
		line = fobj.readline()
		if not line.endswith(b"\n"):
		raise ValueError("Invalid TZif file: unexpected end of file")
		tz_str = line.rstrip(b"\n")
		else:
		tz_str = None

Expand Down
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1,2 @@
		:mod:`zoneinfo`: fix infinite loop in :meth:`ZoneInfo.from_file
		<zoneinfo.ZoneInfo.from_file>` when parsing a malformed TZif file. Patch by Fatih Celik.