diff --git a/airflow-core/src/airflow/api_fastapi/execution_api/routes/task_reschedules.py b/airflow-core/src/airflow/api_fastapi/execution_api/routes/task_reschedules.py
index 3c7d4c8070f34..3930fd945ea45 100644
--- a/airflow-core/src/airflow/api_fastapi/execution_api/routes/task_reschedules.py
+++ b/airflow-core/src/airflow/api_fastapi/execution_api/routes/task_reschedules.py
@@ -19,14 +19,19 @@
 
 from uuid import UUID
 
-from fastapi import APIRouter, status
+from fastapi import APIRouter, Security, status
 from sqlalchemy import select
 
 from airflow.api_fastapi.common.db.common import SessionDep
 from airflow.api_fastapi.common.types import UtcDateTime
+from airflow.api_fastapi.execution_api.security import require_auth
 from airflow.models.taskreschedule import TaskReschedule
 
 router = APIRouter(
+    dependencies=[
+        # Validates that the JWT sub matches the task_instance_id path parameter.
+        Security(require_auth, scopes=["ti:self"]),
+    ],
     responses={
         status.HTTP_404_NOT_FOUND: {"description": "Task Instance not found"},
         status.HTTP_401_UNAUTHORIZED: {"description": "Unauthorized"},
diff --git a/airflow-core/tests/unit/api_fastapi/execution_api/test_app.py b/airflow-core/tests/unit/api_fastapi/execution_api/test_app.py
index 0a71e65525505..2f5a264f4c634 100644
--- a/airflow-core/tests/unit/api_fastapi/execution_api/test_app.py
+++ b/airflow-core/tests/unit/api_fastapi/execution_api/test_app.py
@@ -87,6 +87,49 @@ def test_ct_self_routes_have_connection_test_id_param(client):
                 )
 
 
+# Execution-API routes that expose a {task_instance_id} path parameter but intentionally do NOT
+# enforce the ti:self scope. Add a route here only with a clear justification.
+TI_ID_ROUTES_WITHOUT_TI_SELF: set[str] = set()
+
+
+def test_routes_with_task_instance_id_param_enforce_ti_self(client):
+    """Dual of :func:`test_ti_self_routes_have_task_instance_id_param`.
+
+    Every operation that exposes a ``{task_instance_id}`` path parameter must require the
+    ``ti:self`` scope, so a caller can only act on its own task instance -- unless the path is
+    explicitly listed in ``TI_ID_ROUTES_WITHOUT_TI_SELF``. This guards against a new endpoint
+    accepting a caller-supplied ``task_instance_id`` while silently skipping the ownership check
+    (the bug fixed alongside this test, where ``/task-reschedules/{task_instance_id}/start_date``
+    lacked it). Checked against the served OpenAPI spec of every API version, since the execution
+    API assembles its routes per version.
+    """
+    http_methods = {"get", "put", "post", "delete", "patch", "options", "head", "trace"}
+    offenders = []
+    checked = 0
+    for version in bundle.versions:
+        spec = client.get(f"/execution/openapi.json?version={version.value}").json()
+        for path, operations in spec.get("paths", {}).items():
+            if "{task_instance_id}" not in path or path in TI_ID_ROUTES_WITHOUT_TI_SELF:
+                continue
+            for method, operation in operations.items():
+                if method.lower() not in http_methods or not isinstance(operation, dict):
+                    continue
+                checked += 1
+                requirements = operation.get("security") or []
+                has_ti_self = any(
+                    "ti:self" in scopes for requirement in requirements for scopes in requirement.values()
+                )
+                if not has_ti_self:
+                    offenders.append(f"[{version.value}] {method.upper()} {path}")
+
+    assert checked, "Found no {task_instance_id} operations in any API version -- the test is vacuous."
+    assert not offenders, (
+        "These execution-API operations expose a {task_instance_id} path parameter without the "
+        "ti:self scope. Add `Security(require_auth, scopes=['ti:self'])` to the router, or add the "
+        "path to TI_ID_ROUTES_WITHOUT_TI_SELF with a justification:\n" + "\n".join(sorted(offenders))
+    )
+
+
 class TestCorrelationIdMiddleware:
     def test_correlation_id_echoed_in_response_headers(self, client):
         """Test that correlation-id from request is echoed back in response headers."""