https://github.com/python/cpython/commit/e81960fb82977df7ace77f3c03a3b2d9a0559075
commit: e81960fb82977df7ace77f3c03a3b2d9a0559075
branch: main
author: tonghuaroot (童话) <[email protected]>
committer: StanFromIreland <[email protected]>
date: 2026-08-25T13:20:55+01:00
summary:
gh-152204: Validate date and time fields in
`_pydatetime.date{time}.fromisoformat` (#152205)
Co-authored-by: Stan Ulbrych <[email protected]>
files:
A Misc/NEWS.d/next/Library/2026-06-25-14-05-00.gh-issue-152204.k9Qm3v.rst
M Lib/_pydatetime.py
M Lib/test/datetimetester.py
diff --git a/Lib/_pydatetime.py b/Lib/_pydatetime.py
index c47f4e671b39def..6f53f45d524c991 100644
--- a/Lib/_pydatetime.py
+++ b/Lib/_pydatetime.py
@@ -355,19 +355,30 @@ def _find_isoformat_datetime_separator(dtstr):
return 8
+def _read_isoformat_component(s, n):
+ # The caller has verified the string is ASCII, so isdigit() matches only
+ # the ASCII digits accepted by the C parser.
+ if len(s) != n or not s.isdigit():
+ raise ValueError("Invalid isoformat string")
+ return int(s)
+
+
def _parse_isoformat_date(dtstr):
# It is assumed that this is an ASCII-only string of lengths 7, 8 or 10,
# see the comment on
Modules/_datetimemodule.c:_find_isoformat_datetime_separator
if len(dtstr) not in (7, 8, 10):
raise ValueError("Invalid isoformat string")
- year = int(dtstr[0:4])
+ if not dtstr.isascii():
+ raise ValueError("Invalid isoformat string")
+
+ year = _read_isoformat_component(dtstr[0:4], 4)
has_sep = dtstr[4] == '-'
pos = 4 + has_sep
if dtstr[pos:pos + 1] == "W":
# YYYY-?Www-?D?
pos += 1
- weekno = int(dtstr[pos:pos + 2])
+ weekno = _read_isoformat_component(dtstr[pos:pos + 2], 2)
pos += 2
dayno = 1
@@ -377,17 +388,17 @@ def _parse_isoformat_date(dtstr):
pos += has_sep
- dayno = int(dtstr[pos:pos + 1])
+ dayno = _read_isoformat_component(dtstr[pos:pos + 1], 1)
return list(_isoweek_to_gregorian(year, weekno, dayno))
else:
- month = int(dtstr[pos:pos + 2])
+ month = _read_isoformat_component(dtstr[pos:pos + 2], 2)
pos += 2
if (dtstr[pos:pos + 1] == "-") != has_sep:
raise ValueError("Inconsistent use of dash separator")
pos += has_sep
- day = int(dtstr[pos:pos + 2])
+ day = _read_isoformat_component(dtstr[pos:pos + 2], 2)
return [year, month, day]
@@ -402,10 +413,7 @@ def _parse_hh_mm_ss_ff(tstr):
time_comps = [0, 0, 0, 0]
pos = 0
for comp in range(0, 3):
- if (len_str - pos) < 2:
- raise ValueError("Incomplete time component")
-
- time_comps[comp] = int(tstr[pos:pos+2])
+ time_comps[comp] = _read_isoformat_component(tstr[pos:pos+2], 2)
pos += 2
next_char = tstr[pos:pos+1]
@@ -426,7 +434,7 @@ def _parse_hh_mm_ss_ff(tstr):
raise ValueError("Invalid microsecond separator")
else:
pos += 1
- if not all(map(_is_ascii_digit, tstr[pos:])):
+ if not tstr[pos:].isdigit():
raise ValueError("Non-digit values in fraction")
len_remainder = len_str - pos
@@ -447,6 +455,8 @@ def _parse_isoformat_time(tstr):
len_str = len(tstr)
if len_str < 2:
raise ValueError("Isoformat time too short")
+ if not tstr.isascii():
+ raise ValueError("Invalid isoformat string")
# This is equivalent to re.search('[+-Z]', tstr), but faster
tz_pos = (tstr.find('-') + 1 or tstr.find('+') + 1 or tstr.find('Z') + 1)
diff --git a/Lib/test/datetimetester.py b/Lib/test/datetimetester.py
index c11e9c068bed3bd..dae71a6b6679a0f 100644
--- a/Lib/test/datetimetester.py
+++ b/Lib/test/datetimetester.py
@@ -2106,7 +2106,15 @@ def test_fromisoformat_fails(self):
'10000-W25-1', # Invalid year
'2020-W25-0', # Invalid day-of-week
'2020-W25-8', # Invalid day-of-week
- '٢025-03-09' # Unicode characters
+ # gh-152204: each fixed-width field must be exactly N ASCII digits
+ '2020+12', # '+' in a basic-format field
+ '2020 12', # space in a basic-format field
+ '+020-06-15', # leading sign in the year
+ '202012+9', # '+' in the day field
+ '2020-W 5', # space in the week number
+ '2020061', # 7 chars: day slice reads a 1-character tail
+ '2020-W2', # 1-digit week number
+ '٢025-03-09', # Unicode characters
'2009\ud80002\ud80028', # Separators are surrogate codepoints
]
@@ -3758,6 +3766,15 @@ def test_fromisoformat_fails_datetime(self):
'2009-04-19T12:30:45-00:90:00', # Time zone field out from range
'2009-04-19T12:30:45-00:00:90', # Time zone field out from range
'2020-2020', # Ambiguous 9-char date portion
+ # gh-152204: each time field must be exactly N ASCII digits
+ '2020-12-12T0٥:02:03', # Unicode digit in the hour
+ '2020-12-12T01:0٥:03', # Unicode digit in the minute
+ '2020-12-12T01:02:0٥', # Unicode digit in the second
+ '2020-12-12T01:02:03.٥', # Unicode digit in the fraction
+ '2020-12-12T01:02:03.4_6', # underscore in the fraction
+ '2020-12-12T01:02:03+0٥:00', # Unicode digit in the tz hour
+ '2020-12-12T01:02:03+01:0٥', # Unicode digit in the tz minute
+ '20201212T0102٣٤', # Unicode digits in the
basic-format time
'2009-04-19T12:30:45.+05:00', # Empty fraction before offset
'2009-04-19T12:30:45.-05:00', # Empty fraction before offset
'2009-04-19T12:30:45.Z', # Empty fraction before Z
diff --git
a/Misc/NEWS.d/next/Library/2026-06-25-14-05-00.gh-issue-152204.k9Qm3v.rst
b/Misc/NEWS.d/next/Library/2026-06-25-14-05-00.gh-issue-152204.k9Qm3v.rst
new file mode 100644
index 000000000000000..1ba1f872eb41a61
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2026-06-25-14-05-00.gh-issue-152204.k9Qm3v.rst
@@ -0,0 +1,6 @@
+Fix the pure-Python implementations of :meth:`datetime.date.fromisoformat`,
+:meth:`datetime.time.fromisoformat` and :meth:`datetime.datetime.fromisoformat`
+silently accepting some malformed ISO 8601 strings, such as non-ASCII digits or
+a sign in a fixed-width field (for example ``'2020+12'`` or
``'20201212T0102٣٤'``).
+Each field is now required to be exactly *N* ASCII digits, matching the C
+implementation.
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