From 81e9810428f49fcb470255d2a80c7d2a90e206fc Mon Sep 17 00:00:00 2001
From: Raphael Fakhri <153192858+RaphaelFakhri@users.noreply.github.com>
Date: Wed, 4 Nov 2026 06:35:01 +0000
Subject: [PATCH] gh-139122: Fix the C UUID error message for badly formed hex
 strings

---
 Lib/test/test_uuid.py | 16 ++++++++++++++++
 Modules/_uuidmodule.c | 14 ++++++++------
 2 files changed, 24 insertions(+), 6 deletions(-)

diff --git a/Lib/test/test_uuid.py b/Lib/test/test_uuid.py
index fb278b6c4044c2..9b066e3e32d333 100755
--- a/Lib/test/test_uuid.py
+++ b/Lib/test/test_uuid.py
@@ -311,6 +311,22 @@ def __str__(self):
 
         self.assertEqual(repr(CustomUUID(int=1)), "CustomUUID('custom uuid')")
 
+    def test_bad_hex_error_message(self):
+        # A hex string that does not hold exactly 32 hex digits raises the
+        # same error message in the C and Python implementations.
+        for text in ('',
+                     '1234567812345678123456781234567',
+                     '123456781234567812345678123456789',
+                     '{123456781234567812345678123456789}',
+                     '12345678-1234-5678-1234-567812345678-9',
+                     '12345678-1234-5678-1234-56781234567',
+                     '12345678-1234-5678-1234-5678123456'):
+            with self.subTest(text=text):
+                with self.assertRaises(ValueError) as cm:
+                    self.uuid.UUID(text)
+                self.assertEqual(str(cm.exception),
+                                 'badly formed hexadecimal UUID string')
+
     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 e957071a4ecef9..4acfbc59bc3212 100644
--- a/Modules/_uuidmodule.c
+++ b/Modules/_uuidmodule.c
@@ -738,17 +738,19 @@ from_hex(uuidobject *self, PyObject *hex)
         }
 
         if (j > UUID_SIZE || (j == UUID_SIZE && acc_set)) {
-            PyErr_Format(PyExc_ValueError,
-                "invalid UUID '%s': decodes to more than 16 bytes",
-                hex);
+            PyErr_SetString(
+                PyExc_ValueError,
+                "badly formed hexadecimal UUID string"
+            );
             return -1;
         }
     }
 
     if (j != UUID_SIZE) {
-        PyErr_Format(PyExc_ValueError,
-            "invalid UUID '%s': decodes to less than 16 bytes",
-            hex);
+        PyErr_SetString(
+            PyExc_ValueError,
+            "badly formed hexadecimal UUID string"
+        );
         return -1;
     }