diff --git a/mem0/vector_stores/opensearch.py b/mem0/vector_stores/opensearch.py
index ea8fb4959..8b8b85377 100644
--- a/mem0/vector_stores/opensearch.py
+++ b/mem0/vector_stores/opensearch.py
@@ -1,4 +1,5 @@
 import logging
+import re
 import time
 from typing import Any, Dict, List, Optional
 
@@ -14,6 +15,18 @@ from mem0.vector_stores.base import VectorStoreBase
 
 logger = logging.getLogger(__name__)
 
+_SAFE_FILTER_KEY = re.compile(r"^[a-zA-Z_][a-zA-Z0-9_.]*$")
+
+
+def _validate_filter(key: str, value) -> None:
+    if not isinstance(key, str) or not _SAFE_FILTER_KEY.match(key):
+        raise ValueError(f"Invalid filter key: {key!r}")
+    if not isinstance(value, (str, int, float, bool)):
+        raise ValueError(
+            f"Filter value for {key!r} must be str, int, float, or bool, "
+            f"got {type(value).__name__}"
+        )
+
 
 class OutputData(BaseModel):
     id: str
@@ -196,6 +209,7 @@ class OpenSearchDB(VectorStoreBase):
             for key in ["user_id", "run_id", "agent_id"]:
                 value = filters.get(key)
                 if value:
+                    _validate_filter(key, value)
                     filter_clauses.append({"term": {f"payload.{key}.keyword": value}})
 
         # Combine knn with filters if needed
@@ -246,6 +260,7 @@ class OpenSearchDB(VectorStoreBase):
             for key in ["user_id", "run_id", "agent_id"]:
                 value = filters.get(key)
                 if value:
+                    _validate_filter(key, value)
                     filter_clauses.append({"term": {f"payload.{key}.keyword": value}})
 
         if filter_clauses:
@@ -360,6 +375,7 @@ class OpenSearchDB(VectorStoreBase):
                 for key in ["user_id", "run_id", "agent_id"]:
                     value = filters.get(key)
                     if value:
+                        _validate_filter(key, value)
                         filter_clauses.append({"term": {f"payload.{key}.keyword": value}})
 
             if filter_clauses:
diff --git a/tests/vector_stores/test_opensearch.py b/tests/vector_stores/test_opensearch.py
index a034883f9..6b924e782 100644
--- a/tests/vector_stores/test_opensearch.py
+++ b/tests/vector_stores/test_opensearch.py
@@ -545,3 +545,52 @@ def test_memory_initialization_opensearch_aws_auth(
     assert memory.config.vector_store.provider == "opensearch"
 
     assert mock_vector_factory.call_count >= 2
+
+
+class TestOpenSearchFilterValidation(unittest.TestCase):
+    """Validate that non-scalar filter values are rejected to prevent term injection."""
+
+    def setUp(self):
+        self.client_mock = MagicMock(spec=OpenSearch)
+        self.client_mock.indices = MagicMock()
+        self.client_mock.indices.exists = MagicMock(return_value=False)
+        self.client_mock.indices.create = MagicMock()
+        self.client_mock.search = MagicMock()
+
+        patcher = patch("mem0.vector_stores.opensearch.OpenSearch", return_value=self.client_mock)
+        self.mock_os = patcher.start()
+        self.addCleanup(patcher.stop)
+
+        self.os_db = OpenSearchDB(
+            host="localhost",
+            port=9200,
+            collection_name="test_collection",
+            embedding_model_dims=1536,
+            verify_certs=False,
+            use_ssl=False,
+        )
+        self.client_mock.reset_mock()
+
+    def test_search_rejects_dict_filter_value(self):
+        with self.assertRaises(ValueError):
+            self.os_db.search(query="", vectors=[[0.1] * 1536], filters={"user_id": {"$ne": ""}})
+
+    def test_search_rejects_list_filter_value(self):
+        with self.assertRaises(ValueError):
+            self.os_db.search(query="", vectors=[[0.1] * 1536], filters={"user_id": ["alice", "bob"]})
+
+    def test_list_rejects_dict_filter_value(self):
+        result = self.os_db.list(filters={"user_id": {"$ne": ""}})
+        self.assertEqual(result, [[]])
+        self.client_mock.search.assert_not_called()
+
+    def test_keyword_search_rejects_dict_filter_value(self):
+        with self.assertRaises(ValueError):
+            self.os_db.keyword_search(query="test", filters={"user_id": {"$ne": ""}})
+
+    def test_search_accepts_string_filter(self):
+        mock_response = {"hits": {"hits": []}}
+        self.client_mock.search.return_value = mock_response
+        results = self.os_db.search(query="", vectors=[[0.1] * 1536], filters={"user_id": "alice"})
+        self.assertEqual(results, [])
+        self.client_mock.search.assert_called_once()