diff --git a/pkg/config/control_plane.go b/pkg/config/control_plane.go
index 4475ec83b8..ccd4a6d136 100644
--- a/pkg/config/control_plane.go
+++ b/pkg/config/control_plane.go
@@ -77,7 +77,10 @@ func (s *SharedSSOConfig) UnmarshalJSON(data []byte) error {
 		return err
 	}
 
-	provider := m["provider"].(string)
+	provider, ok := m["provider"].(string)
+	if !ok {
+		return fmt.Errorf("provider field in SharedSSOConfig must be a string, got %T", m["provider"])
+	}
 	v, ok := model.ProjectSSOConfig_Provider_value[provider]
 	if !ok {
 		return fmt.Errorf("unsupported provider %s", provider)
@@ -88,7 +91,11 @@ func (s *SharedSSOConfig) UnmarshalJSON(data []byte) error {
 	if !ok {
 		return fmt.Errorf("name field in SharedSSOConfig is required")
 	}
-	s.Name = name.(string)
+	nameStr, ok := name.(string)
+	if !ok {
+		return fmt.Errorf("name field in SharedSSOConfig must be a string, got %T", name)
+	}
+	s.Name = nameStr
 	delete(m, "name")
 
 	data, err := json.Marshal(m)
diff --git a/pkg/config/shared_sso_config_test.go b/pkg/config/shared_sso_config_test.go
new file mode 100644
index 0000000000..d086248eec
--- /dev/null
+++ b/pkg/config/shared_sso_config_test.go
@@ -0,0 +1,42 @@
+// Copyright 2024 The PipeCD Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package config
+
+import (
+	"encoding/json"
+	"testing"
+)
+
+// Each body previously panicked in UnmarshalJSON, which decodes into
+// map[string]interface{} and asserts on the lookups.
+func TestSharedSSOConfigMalformed(t *testing.T) {
+	for name, body := range map[string]string{
+		"provider missing":  `{"name":"github"}`,
+		"provider a number": `{"name":"github","provider":42}`,
+		"name a number":     `{"name":42,"provider":"GITHUB"}`,
+	} {
+		t.Run(name, func(t *testing.T) {
+			defer func() {
+				if r := recover(); r != nil {
+					t.Fatalf("panicked on user config: %v", r)
+				}
+			}()
+			var c SharedSSOConfig
+			if err := json.Unmarshal([]byte(body), &c); err == nil {
+				t.Fatal("want an error, got nil")
+			}
+		})
+	}
+}
diff --git a/pkg/configv1/control_plane.go b/pkg/configv1/control_plane.go
index 4475ec83b8..ccd4a6d136 100644
--- a/pkg/configv1/control_plane.go
+++ b/pkg/configv1/control_plane.go
@@ -77,7 +77,10 @@ func (s *SharedSSOConfig) UnmarshalJSON(data []byte) error {
 		return err
 	}
 
-	provider := m["provider"].(string)
+	provider, ok := m["provider"].(string)
+	if !ok {
+		return fmt.Errorf("provider field in SharedSSOConfig must be a string, got %T", m["provider"])
+	}
 	v, ok := model.ProjectSSOConfig_Provider_value[provider]
 	if !ok {
 		return fmt.Errorf("unsupported provider %s", provider)
@@ -88,7 +91,11 @@ func (s *SharedSSOConfig) UnmarshalJSON(data []byte) error {
 	if !ok {
 		return fmt.Errorf("name field in SharedSSOConfig is required")
 	}
-	s.Name = name.(string)
+	nameStr, ok := name.(string)
+	if !ok {
+		return fmt.Errorf("name field in SharedSSOConfig must be a string, got %T", name)
+	}
+	s.Name = nameStr
 	delete(m, "name")
 
 	data, err := json.Marshal(m)
diff --git a/pkg/configv1/shared_sso_config_test.go b/pkg/configv1/shared_sso_config_test.go
new file mode 100644
index 0000000000..d086248eec
--- /dev/null
+++ b/pkg/configv1/shared_sso_config_test.go
@@ -0,0 +1,42 @@
+// Copyright 2024 The PipeCD Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package config
+
+import (
+	"encoding/json"
+	"testing"
+)
+
+// Each body previously panicked in UnmarshalJSON, which decodes into
+// map[string]interface{} and asserts on the lookups.
+func TestSharedSSOConfigMalformed(t *testing.T) {
+	for name, body := range map[string]string{
+		"provider missing":  `{"name":"github"}`,
+		"provider a number": `{"name":"github","provider":42}`,
+		"name a number":     `{"name":42,"provider":"GITHUB"}`,
+	} {
+		t.Run(name, func(t *testing.T) {
+			defer func() {
+				if r := recover(); r != nil {
+					t.Fatalf("panicked on user config: %v", r)
+				}
+			}()
+			var c SharedSSOConfig
+			if err := json.Unmarshal([]byte(body), &c); err == nil {
+				t.Fatal("want an error, got nil")
+			}
+		})
+	}
+}