00475: CVE-2025-15367

pythongh-143923: Reject control characters in POP3 commands

(cherry-picked from commit b234a2b)

Author: sethmlarson

Lib/poplib.py

@@ -117,6 +117,8 @@ def _putline(self, line):
     def _putcmd(self, line):
         if self._debugging: print('*cmd*', repr(line))
         line = bytes(line, self.encoding)
+        if re.search(b'[\x00-\x1F\x7F]', line):
+            raise ValueError('Control characters not allowed in commands')
         self._putline(line)
 
 

Lib/test/test_poplib.py

@@ -12,6 +12,7 @@
 
 from unittest import TestCase, skipUnless
 from test import support as test_support
+from test.support import control_characters_c0
 threading = test_support.import_module('threading')
 
 HOST = test_support.HOST
@@ -349,6 +350,13 @@ def test_quit(self):
         self.assertIsNone(self.client.sock)
         self.assertIsNone(self.client.file)
 
+    def test_control_characters(self):
+        for c0 in control_characters_c0():
+            with self.assertRaises(ValueError):
+                self.client.user(f'user{c0}')
+            with self.assertRaises(ValueError):
+                self.client.pass_(f'{c0}pass')
+
     @requires_ssl
     def test_stls_capa(self):
         capa = self.client.capa()

Misc/NEWS.d/next/Security/2026-01-16-11-43-47.gh-issue-143923.DuytMe.rst

@@ -0,0 +1 @@
+Reject control characters in POP3 commands.