gh-99453: improve entries validation of Netscape/Mozilla cookie files

Lib/http/cookiejar.py

@@ -2037,8 +2037,10 @@ def _really_load(self, f, filename, ignore_discard, ignore_expires):
                     line.strip() == ""):
                     continue
 
-                domain, domain_specified, path, secure, expires, name, value = \
-                        line.split("\t")
+                fields = line.split("\t")
+                if len(fields) != 7:
+                    raise LoadError("invalid fields in Netscape format cookies file %r: %r" % (filename, line))
+                domain, domain_specified, path, secure, expires, name, value = fields
                 secure = (secure == "TRUE")
                 domain_specified = (domain_specified == "TRUE")
                 if name == "":

Lib/test/test_http_cookiejar.py

@@ -2023,6 +2023,19 @@ def test_session_cookies(self):
             # we didn't have session cookies in the first place
         self.assertNotEqual(counter["session_before"], 0)
 
+    def test_mozilla_cookiejar_loaderror_on_malformed_file(self):
+        # Malformed cookie file should raise LoadError
+        filename = os_helper.TESTFN
+        with open(filename, "w") as f:
+            f.write("# Netscape HTTP Cookie File\ninvalid_line\n")
+        jar = MozillaCookieJar(filename)
+        try:
+            with self.assertRaisesRegex(LoadError, "invalid fields in Netscape format cookies file"):
+                jar.load()
+        finally:
+            os_helper.unlink(filename)
+
+
 
 if __name__ == "__main__":
     unittest.main()

Misc/ACKS

@@ -1534,6 +1534,7 @@ Kirill (python273) R.
 Abhilash Raj
 Shorya Raj
 Ajith Ramachandran
+Paul Ramshaw
 Dhushyanth Ramasamy
 Ashwin Ramaswami
 Jeff Ramnani

Misc/NEWS.d/next/Library/2025-09-28-12-52-40.gh-issue-99453.qJBIf-.rst

@@ -0,0 +1,2 @@
+**http.cookiejar**: Netscape/Mozilla cookie files with malformed lines now
+raise :exc:`LoadError` instead of an uncaught :exc:`ValueError`.