From 5d00096f828427afbfc2f283c7c5cb099ab3f7fa Mon Sep 17 00:00:00 2001
From: "Gina A." <70909035+gndz07@users.noreply.github.com>
Date: Wed, 7 Jan 2026 09:38:05 +0100
Subject: [PATCH] Fix panic for empty defaultBackend and defaultBackend without
 resources

---
 ...ress-with-defaultbackend-with-resource.yml | 12 +++++++++++
 .../Ingress-with-empty-defaultbackend.yml     |  8 ++++++++
 pkg/provider/kubernetes/ingress/kubernetes.go | 11 ++++++++++
 .../kubernetes/ingress/kubernetes_test.go     | 20 +++++++++++++++++++
 4 files changed, 51 insertions(+)
 create mode 100644 pkg/provider/kubernetes/ingress/fixtures/Ingress-with-defaultbackend-with-resource.yml
 create mode 100644 pkg/provider/kubernetes/ingress/fixtures/Ingress-with-empty-defaultbackend.yml

diff --git a/pkg/provider/kubernetes/ingress/fixtures/Ingress-with-defaultbackend-with-resource.yml b/pkg/provider/kubernetes/ingress/fixtures/Ingress-with-defaultbackend-with-resource.yml
new file mode 100644
index 000000000..2d21ccab4
--- /dev/null
+++ b/pkg/provider/kubernetes/ingress/fixtures/Ingress-with-defaultbackend-with-resource.yml
@@ -0,0 +1,12 @@
+kind: Ingress
+apiVersion: networking.k8s.io/v1
+metadata:
+  name: defaultbackend
+  namespace: testing
+
+spec:
+  defaultBackend:
+    resource:
+      apiGroup: example.com
+      kind: SomeBackend
+      name: foo
diff --git a/pkg/provider/kubernetes/ingress/fixtures/Ingress-with-empty-defaultbackend.yml b/pkg/provider/kubernetes/ingress/fixtures/Ingress-with-empty-defaultbackend.yml
new file mode 100644
index 000000000..9eff4acd5
--- /dev/null
+++ b/pkg/provider/kubernetes/ingress/fixtures/Ingress-with-empty-defaultbackend.yml
@@ -0,0 +1,8 @@
+kind: Ingress
+apiVersion: networking.k8s.io/v1
+metadata:
+  name: defaultbackend
+  namespace: testing
+
+spec:
+  defaultBackend: {}
diff --git a/pkg/provider/kubernetes/ingress/kubernetes.go b/pkg/provider/kubernetes/ingress/kubernetes.go
index 775ff2a7d..fa0afe5d5 100644
--- a/pkg/provider/kubernetes/ingress/kubernetes.go
+++ b/pkg/provider/kubernetes/ingress/kubernetes.go
@@ -269,6 +269,17 @@ func (p *Provider) loadConfigurationFromIngresses(ctx context.Context, client Cl
 				continue
 			}
 
+			if ingress.Spec.DefaultBackend.Resource != nil {
+				// https://kubernetes.io/docs/concepts/services-networking/ingress/#resource-backend
+				logger.Error().Msg("Resource is not supported for default backend")
+				continue
+			}
+
+			if ingress.Spec.DefaultBackend.Service == nil {
+				logger.Error().Msg("Default backend is missing service definition")
+				continue
+			}
+
 			service, err := p.loadService(client, ingress.Namespace, *ingress.Spec.DefaultBackend)
 			if err != nil {
 				logger.Error().
diff --git a/pkg/provider/kubernetes/ingress/kubernetes_test.go b/pkg/provider/kubernetes/ingress/kubernetes_test.go
index 0b95bf173..c67e84e57 100644
--- a/pkg/provider/kubernetes/ingress/kubernetes_test.go
+++ b/pkg/provider/kubernetes/ingress/kubernetes_test.go
@@ -550,6 +550,26 @@ func TestLoadConfigurationFromIngresses(t *testing.T) {
 				},
 			},
 		},
+		{
+			desc: "Ingress with defaultbackend with resource",
+			expected: &dynamic.Configuration{
+				HTTP: &dynamic.HTTPConfiguration{
+					Middlewares: map[string]*dynamic.Middleware{},
+					Routers:     map[string]*dynamic.Router{},
+					Services:    map[string]*dynamic.Service{},
+				},
+			},
+		},
+		{
+			desc: "Ingress with empty defaultbackend",
+			expected: &dynamic.Configuration{
+				HTTP: &dynamic.HTTPConfiguration{
+					Middlewares: map[string]*dynamic.Middleware{},
+					Routers:     map[string]*dynamic.Router{},
+					Services:    map[string]*dynamic.Service{},
+				},
+			},
+		},
 		{
 			desc: "Ingress with one service without endpoint",
 			expected: &dynamic.Configuration{