From 08806a68f2ab0d92853c08ce50a907f10c0a4c46 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?tonghuaroot=20=28=E7=AB=A5=E8=AF=9D=29?=
 <tonghuaroot@gmail.com>
Date: Sat, 24 Oct 2026 14:57:12 +0800
Subject: [PATCH] gh-139122: Reset the cached hash of C UUIDs in __init__ and
 __setstate__

Subclass instances are allocated zeroed, so cached_hash started at 0 and
hash() returned 0. Re-initializing an existing UUID also kept the old
hash.
---
 Lib/test/test_uuid.py | 28 ++++++++++++++++++++++++++++
 Modules/_uuidmodule.c |  2 ++
 2 files changed, 30 insertions(+)
 mode change 100755 => 100644 Lib/test/test_uuid.py

diff --git a/Lib/test/test_uuid.py b/Lib/test/test_uuid.py
old mode 100755
new mode 100644
index ee6e57b93966a23..bbbc7fbad7e7b42
--- a/Lib/test/test_uuid.py
+++ b/Lib/test/test_uuid.py
@@ -311,6 +311,34 @@ def __str__(self):
 
         self.assertEqual(repr(CustomUUID(int=1)), "CustomUUID('custom uuid')")
 
+    def test_hash_subclass_and_reinit(self):
+        class CustomUUID(self.uuid.UUID):
+            pass
+
+        with support.swap_item(sys.modules, 'uuid', self.uuid):
+            for value in (0, 1, 0x12345678123456781234567812345678):
+                with self.subTest(value=value):
+                    u = self.uuid.UUID(int=value)
+                    expected = hash(u)
+
+                    s = CustomUUID(int=value)
+                    self.assertEqual(hash(s), expected)
+                    self.assertIn(u, {s})
+
+                    s = CustomUUID.__new__(CustomUUID)
+                    s.__setstate__({'int': value})
+                    self.assertEqual(hash(s), expected)
+
+                    u = self.uuid.UUID(int=value + 1)
+                    hash(u)
+                    u.__init__(int=value)
+                    self.assertEqual(hash(u), expected)
+
+                    u = self.uuid.UUID(int=value + 1)
+                    hash(u)
+                    u.__setstate__({'int': value})
+                    self.assertEqual(hash(u), expected)
+
     def test_exceptions(self):
         badvalue = lambda f: self.assertRaises(ValueError, f)
         badtype = lambda f: self.assertRaises(TypeError, f)
diff --git a/Modules/_uuidmodule.c b/Modules/_uuidmodule.c
index e957071a4ecef95..00402280d6e2c94 100644
--- a/Modules/_uuidmodule.c
+++ b/Modules/_uuidmodule.c
@@ -628,6 +628,7 @@ _uuid_UUID___init___impl(uuidobject *self, PyObject *hex, PyObject *bytes,
         self->bytes[6] |= (uint8_t)(version_num << 4);
     }
 
+    self->cached_hash = -1;
     Py_XSETREF(self->is_safe, Py_XNewRef(is_safe));
 
     return 0;
@@ -1655,6 +1656,7 @@ _uuid_UUID___setstate___impl(uuidobject *self, PyObject *state)
     if (result < 0) {
         return NULL;
     }
+    self->cached_hash = -1;
 
     int has_is_safe = PySequence_Contains(state, &_Py_ID(is_safe));
     if (has_is_safe < 0) {