Elide the looong value in the exception message.

Author: gpshead

Lib/ipaddress.py

@@ -1661,7 +1661,8 @@ def _ip_int_from_string(cls, ip_str):
         if not ip_str:
             raise AddressValueError('Address cannot be empty')
         if len(ip_str) > 39:
-            msg = "At most 39 characters expected in %r" % (ip_str,)
+            msg = ("At most 39 characters expected in "
+                   f"{ip_str[:14]!r}({len(ip_str)-28} chars elided){ip_str[-14:]!r}")
             raise AddressValueError(msg)
 
         # We want to allow more parts than the max to be 'split'

Lib/test/test_ipaddress.py

@@ -399,8 +399,8 @@ def assertBadSplit(addr):
 
     def test_bad_address_split_v6_too_long(self):
         def assertBadSplit(addr):
-            msg = "At most 39 characters expected in %r"
-            with self.assertAddressError(msg, addr.split('%')[0]):
+            msg = r"At most 39 characters expected in %s"
+            with self.assertAddressError(msg, repr(re.escape(addr[:14]))):
                 ipaddress.IPv6Address(addr)
 
         # Long IPv6 address

Misc/NEWS.d/next/Security/2025-01-14-11-19-07.gh-issue-128840.M1doZW.rst

@@ -1,2 +1,2 @@
-Short-circuit the processing of long IPv6 addresses early to prevent excessive
+Short-circuit the processing of long IPv6 addresses early in :mod:`ipaddress` to prevent excessive
 memory consumption and a minor denial-of-service.