From d7067f7062f9d620825fef301b942e280cb439b7 Mon Sep 17 00:00:00 2001
From: Andrew Halaney <ahalaney@netflix.com>
Date: Tue, 5 May 2026 14:21:19 -0500
Subject: [PATCH] Fix InstanceMetadataRegionFetcher for local zones

InstanceMetadataRegionFetcher queries latest/meta-data/placement/availability-zone/
and strips the trailing character to derive the region. This works for
standard AZs (us-east-1a becomes us-east-1) but breaks for local zones
(us-east-1-atl-2a becomes us-east-1-atl-2).

Switch to latest/meta-data/placement/region, which returns the parent
region directly. This has been around since[0] 2020 so it _should_ be ok to
use.

[0]: https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/ec2-instance-metadata.html#instancedata-data-categories
---
 botocore/utils.py        |  6 ++----
 tests/unit/test_utils.py | 34 ++++++++++++++++++++++++++++++++++
 2 files changed, 36 insertions(+), 4 deletions(-)

diff --git a/botocore/utils.py b/botocore/utils.py
index 9553e0c82a..47b5d88c04 100644
--- a/botocore/utils.py
+++ b/botocore/utils.py
@@ -783,7 +783,7 @@ def _create_fetcher(self):
 
 
 class InstanceMetadataRegionFetcher(IMDSFetcher):
-    _URL_PATH = 'latest/meta-data/placement/availability-zone/'
+    _URL_PATH = 'latest/meta-data/placement/region'
 
     def retrieve_region(self):
         """Get the current region from the instance metadata service.
@@ -815,9 +815,7 @@ def _get_region(self):
             retry_func=self._default_retry,
             token=token,
         )
-        availability_zone = response.text
-        region = availability_zone[:-1]
-        return region
+        return response.text
 
 
 def merge_dicts(dict1, dict2, append_lists=False):
diff --git a/tests/unit/test_utils.py b/tests/unit/test_utils.py
index 96a485a1c2..d5cf536a51 100644
--- a/tests/unit/test_utils.py
+++ b/tests/unit/test_utils.py
@@ -3372,6 +3372,40 @@ def test_expiry_extension_with_bad_datetime(self):
         assert results['expiry_time'] == bad_datetime
 
 
+class TestInstanceMetadataRegionFetcher(unittest.TestCase):
+    _IMDS_RESPONSES = {
+        'api/token': b'my-token',
+        'placement/region': b'us-east-1',
+        'placement/availability-zone': b'us-east-1-atl-2a',
+    }
+
+    def setUp(self):
+        urllib3_session_send = 'botocore.httpsession.URLLib3Session.send'
+        self._urllib3_patch = mock.patch(urllib3_session_send)
+        self._send = self._urllib3_patch.start()
+        self._send.side_effect = self._get_imds_response
+
+    def tearDown(self):
+        self._urllib3_patch.stop()
+
+    def _get_imds_response(self, request):
+        for path, body in self._IMDS_RESPONSES.items():
+            if path in request.url:
+                return botocore.awsrequest.AWSResponse(
+                    url=request.url,
+                    status_code=200,
+                    headers={},
+                    raw=RawResponse(body),
+                )
+        raise ValueError(f'Unexpected IMDS request: {request.url}')
+
+    def _make_fetcher(self):
+        return InstanceMetadataRegionFetcher()
+
+    def test_retrieve_region_local_zone_instance(self):
+        self.assertEqual(self._make_fetcher().retrieve_region(), 'us-east-1')
+
+
 class TestIMDSRegionProvider(unittest.TestCase):
     def setUp(self):
         self.environ = {}