https://github.com/python/cpython/commit/f7fceed79ca1bceae8dbe5ba5bc8928564da7211
commit: f7fceed79ca1bceae8dbe5ba5bc8928564da7211
branch: main
author: Seth Michael Larson <[email protected]>
committer: gpshead <[email protected]>
date: 2026-01-17T09:46:21-08:00
summary:
gh-143916: Reject control characters in wsgiref.headers.Headers (GH-143917)
* Add 'test.support' fixture for C0 control characters
* gh-143916: Reject control characters in wsgiref.headers.Headers
files:
A Misc/NEWS.d/next/Security/2026-01-16-11-07-36.gh-issue-143916.dpWeOD.rst
M Lib/test/support/__init__.py
M Lib/test/test_wsgiref.py
M Lib/wsgiref/headers.py
diff --git a/Lib/test/support/__init__.py b/Lib/test/support/__init__.py
index 3a639497fa1272..9c113a6c137e52 100644
--- a/Lib/test/support/__init__.py
+++ b/Lib/test/support/__init__.py
@@ -3303,3 +3303,10 @@ def linked_to_musl():
return _linked_to_musl
_linked_to_musl = tuple(map(int, version.split('.')))
return _linked_to_musl
+
+
+def control_characters_c0() -> list[str]:
+ """Returns a list of C0 control characters as strings.
+ C0 control characters defined as the byte range 0x00-0x1F, and 0x7F.
+ """
+ return [chr(c) for c in range(0x00, 0x20)] + ["\x7F"]
diff --git a/Lib/test/test_wsgiref.py b/Lib/test/test_wsgiref.py
index a8f71c636f9cca..d24aaab1327409 100644
--- a/Lib/test/test_wsgiref.py
+++ b/Lib/test/test_wsgiref.py
@@ -1,6 +1,6 @@
from unittest import mock
from test import support
-from test.support import socket_helper
+from test.support import socket_helper, control_characters_c0
from test.test_httpservers import NoLogRequestHandler
from unittest import TestCase
from wsgiref.util import setup_testing_defaults
@@ -503,6 +503,16 @@ def testExtras(self):
'\r\n'
)
+ def testRaisesControlCharacters(self):
+ headers = Headers()
+ for c0 in control_characters_c0():
+ self.assertRaises(ValueError, headers.__setitem__, f"key{c0}",
"val")
+ self.assertRaises(ValueError, headers.__setitem__, "key",
f"val{c0}")
+ self.assertRaises(ValueError, headers.add_header, f"key{c0}",
"val", param="param")
+ self.assertRaises(ValueError, headers.add_header, "key",
f"val{c0}", param="param")
+ self.assertRaises(ValueError, headers.add_header, "key", "val",
param=f"param{c0}")
+
+
class ErrorHandler(BaseCGIHandler):
"""Simple handler subclass for testing BaseHandler"""
diff --git a/Lib/wsgiref/headers.py b/Lib/wsgiref/headers.py
index c78879f80c7df2..e180a623cb2c30 100644
--- a/Lib/wsgiref/headers.py
+++ b/Lib/wsgiref/headers.py
@@ -9,6 +9,7 @@
# existence of which force quoting of the parameter value.
import re
tspecials = re.compile(r'[ \(\)<>@,;:\\"/\[\]\?=]')
+_control_chars_re = re.compile(r'[\x00-\x1F\x7F]')
def _formatparam(param, value=None, quote=1):
"""Convenience function to format and return a key=value pair.
@@ -41,6 +42,8 @@ def __init__(self, headers=None):
def _convert_string_type(self, value):
"""Convert/check value type."""
if type(value) is str:
+ if _control_chars_re.search(value):
+ raise ValueError("Control characters not allowed in headers")
return value
raise AssertionError("Header names/values must be"
" of type str (got {0})".format(repr(value)))
diff --git
a/Misc/NEWS.d/next/Security/2026-01-16-11-07-36.gh-issue-143916.dpWeOD.rst
b/Misc/NEWS.d/next/Security/2026-01-16-11-07-36.gh-issue-143916.dpWeOD.rst
new file mode 100644
index 00000000000000..44bd0b27059f94
--- /dev/null
+++ b/Misc/NEWS.d/next/Security/2026-01-16-11-07-36.gh-issue-143916.dpWeOD.rst
@@ -0,0 +1,2 @@
+Reject C0 control characters within wsgiref.headers.Headers fields, values,
+and parameters.
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