diff --git a/CHANGELOG.md b/CHANGELOG.md
index 3c409f100..ce7e19ad6 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -424,6 +424,9 @@
     - **Dependencies:** Bump STACKIT SDK core module from `v0.24.1` to `v0.25.0`
   - [v0.5.2](services/vpn/CHANGELOG.md#v052)
     - **Dependencies:** Bump STACKIT SDK core module to `v0.26.0`
+  - [v0.6.0](services/vpn/CHANGELOG.md#v060)
+    - **Feature:** Added `_UNKNOWN_DEFAULT_OPEN_API` fallback value to all enums to handle unknown API values gracefully.
+
 
 ## Release (2026-04-07)
 - `alb`: [v0.13.1](services/alb/CHANGELOG.md#v0131)
diff --git a/services/vpn/CHANGELOG.md b/services/vpn/CHANGELOG.md
index 9b0888744..8b4a721cc 100644
--- a/services/vpn/CHANGELOG.md
+++ b/services/vpn/CHANGELOG.md
@@ -1,3 +1,6 @@
+## v0.6.0
+- **Feature:** Added `_UNKNOWN_DEFAULT_OPEN_API` fallback value to all enums to handle unknown API values gracefully.
+
 ## v0.5.2
 - **Dependencies:** Bump STACKIT SDK core module to `v0.26.0`
 
diff --git a/services/vpn/VERSION b/services/vpn/VERSION
index b0c2058e6..e07d136c7 100644
--- a/services/vpn/VERSION
+++ b/services/vpn/VERSION
@@ -1 +1 @@
-v0.5.2
+v0.6.0
\ No newline at end of file
diff --git a/services/vpn/oas_commit b/services/vpn/oas_commit
index 6ffe07488..6fdb25c73 100644
--- a/services/vpn/oas_commit
+++ b/services/vpn/oas_commit
@@ -1 +1 @@
-f133408fd6686f12ba34f400ba631124b063f5cc
+c8e6adbf2c24050dca06a64b301b3a43ba28be6e
diff --git a/services/vpn/v1alpha1api/model_gateway_status.go b/services/vpn/v1alpha1api/model_gateway_status.go
index 40c51f3b8..ca001a98c 100644
--- a/services/vpn/v1alpha1api/model_gateway_status.go
+++ b/services/vpn/v1alpha1api/model_gateway_status.go
@@ -20,10 +20,11 @@ type GatewayStatus string
 
 // List of GatewayStatus
 const (
-	GATEWAYSTATUS_PENDING  GatewayStatus = "PENDING"
-	GATEWAYSTATUS_READY    GatewayStatus = "READY"
-	GATEWAYSTATUS_ERROR    GatewayStatus = "ERROR"
-	GATEWAYSTATUS_DELETING GatewayStatus = "DELETING"
+	GATEWAYSTATUS_PENDING                  GatewayStatus = "PENDING"
+	GATEWAYSTATUS_READY                    GatewayStatus = "READY"
+	GATEWAYSTATUS_ERROR                    GatewayStatus = "ERROR"
+	GATEWAYSTATUS_DELETING                 GatewayStatus = "DELETING"
+	GATEWAYSTATUS_UNKNOWN_DEFAULT_OPEN_API GatewayStatus = "unknown_default_open_api"
 )
 
 // All allowed values of GatewayStatus enum
@@ -32,6 +33,7 @@ var AllowedGatewayStatusEnumValues = []GatewayStatus{
 	"READY",
 	"ERROR",
 	"DELETING",
+	"unknown_default_open_api",
 }
 
 func (v *GatewayStatus) UnmarshalJSON(src []byte) error {
@@ -48,7 +50,8 @@ func (v *GatewayStatus) UnmarshalJSON(src []byte) error {
 		}
 	}
 
-	return fmt.Errorf("%+v is not a valid GatewayStatus", value)
+	*v = GATEWAYSTATUS_UNKNOWN_DEFAULT_OPEN_API
+	return nil
 }
 
 // NewGatewayStatusFromValue returns a pointer to a valid GatewayStatus
diff --git a/services/vpn/v1alpha1api/model_region.go b/services/vpn/v1alpha1api/model_region.go
index 8bbca0bcb..e78524324 100644
--- a/services/vpn/v1alpha1api/model_region.go
+++ b/services/vpn/v1alpha1api/model_region.go
@@ -20,14 +20,16 @@ type Region string
 
 // List of Region
 const (
-	REGION_EU01 Region = "eu01"
-	REGION_EU02 Region = "eu02"
+	REGION_EU01                     Region = "eu01"
+	REGION_EU02                     Region = "eu02"
+	REGION_UNKNOWN_DEFAULT_OPEN_API Region = "unknown_default_open_api"
 )
 
 // All allowed values of Region enum
 var AllowedRegionEnumValues = []Region{
 	"eu01",
 	"eu02",
+	"unknown_default_open_api",
 }
 
 func (v *Region) UnmarshalJSON(src []byte) error {
@@ -44,7 +46,8 @@ func (v *Region) UnmarshalJSON(src []byte) error {
 		}
 	}
 
-	return fmt.Errorf("%+v is not a valid Region", value)
+	*v = REGION_UNKNOWN_DEFAULT_OPEN_API
+	return nil
 }
 
 // NewRegionFromValue returns a pointer to a valid Region
diff --git a/services/vpn/v1alpha1api/model_routing_type.go b/services/vpn/v1alpha1api/model_routing_type.go
index 07ecc1988..bad95fd38 100644
--- a/services/vpn/v1alpha1api/model_routing_type.go
+++ b/services/vpn/v1alpha1api/model_routing_type.go
@@ -20,9 +20,10 @@ type RoutingType string
 
 // List of RoutingType
 const (
-	ROUTINGTYPE_POLICY_BASED    RoutingType = "POLICY_BASED"
-	ROUTINGTYPE_ROUTE_BASED     RoutingType = "ROUTE_BASED"
-	ROUTINGTYPE_BGP_ROUTE_BASED RoutingType = "BGP_ROUTE_BASED"
+	ROUTINGTYPE_POLICY_BASED             RoutingType = "POLICY_BASED"
+	ROUTINGTYPE_ROUTE_BASED              RoutingType = "ROUTE_BASED"
+	ROUTINGTYPE_BGP_ROUTE_BASED          RoutingType = "BGP_ROUTE_BASED"
+	ROUTINGTYPE_UNKNOWN_DEFAULT_OPEN_API RoutingType = "unknown_default_open_api"
 )
 
 // All allowed values of RoutingType enum
@@ -30,6 +31,7 @@ var AllowedRoutingTypeEnumValues = []RoutingType{
 	"POLICY_BASED",
 	"ROUTE_BASED",
 	"BGP_ROUTE_BASED",
+	"unknown_default_open_api",
 }
 
 func (v *RoutingType) UnmarshalJSON(src []byte) error {
@@ -46,7 +48,8 @@ func (v *RoutingType) UnmarshalJSON(src []byte) error {
 		}
 	}
 
-	return fmt.Errorf("%+v is not a valid RoutingType", value)
+	*v = ROUTINGTYPE_UNKNOWN_DEFAULT_OPEN_API
+	return nil
 }
 
 // NewRoutingTypeFromValue returns a pointer to a valid RoutingType
diff --git a/services/vpn/v1beta1api/model_gateway_status.go b/services/vpn/v1beta1api/model_gateway_status.go
index 5f8036b36..2c0689e1b 100644
--- a/services/vpn/v1beta1api/model_gateway_status.go
+++ b/services/vpn/v1beta1api/model_gateway_status.go
@@ -20,10 +20,11 @@ type GatewayStatus string
 
 // List of GatewayStatus
 const (
-	GATEWAYSTATUS_PENDING  GatewayStatus = "PENDING"
-	GATEWAYSTATUS_READY    GatewayStatus = "READY"
-	GATEWAYSTATUS_ERROR    GatewayStatus = "ERROR"
-	GATEWAYSTATUS_DELETING GatewayStatus = "DELETING"
+	GATEWAYSTATUS_PENDING                  GatewayStatus = "PENDING"
+	GATEWAYSTATUS_READY                    GatewayStatus = "READY"
+	GATEWAYSTATUS_ERROR                    GatewayStatus = "ERROR"
+	GATEWAYSTATUS_DELETING                 GatewayStatus = "DELETING"
+	GATEWAYSTATUS_UNKNOWN_DEFAULT_OPEN_API GatewayStatus = "unknown_default_open_api"
 )
 
 // All allowed values of GatewayStatus enum
@@ -32,6 +33,7 @@ var AllowedGatewayStatusEnumValues = []GatewayStatus{
 	"READY",
 	"ERROR",
 	"DELETING",
+	"unknown_default_open_api",
 }
 
 func (v *GatewayStatus) UnmarshalJSON(src []byte) error {
@@ -48,7 +50,8 @@ func (v *GatewayStatus) UnmarshalJSON(src []byte) error {
 		}
 	}
 
-	return fmt.Errorf("%+v is not a valid GatewayStatus", value)
+	*v = GATEWAYSTATUS_UNKNOWN_DEFAULT_OPEN_API
+	return nil
 }
 
 // NewGatewayStatusFromValue returns a pointer to a valid GatewayStatus
diff --git a/services/vpn/v1beta1api/model_region.go b/services/vpn/v1beta1api/model_region.go
index 5c9e26479..948ed2c73 100644
--- a/services/vpn/v1beta1api/model_region.go
+++ b/services/vpn/v1beta1api/model_region.go
@@ -20,14 +20,16 @@ type Region string
 
 // List of Region
 const (
-	REGION_EU01 Region = "eu01"
-	REGION_EU02 Region = "eu02"
+	REGION_EU01                     Region = "eu01"
+	REGION_EU02                     Region = "eu02"
+	REGION_UNKNOWN_DEFAULT_OPEN_API Region = "unknown_default_open_api"
 )
 
 // All allowed values of Region enum
 var AllowedRegionEnumValues = []Region{
 	"eu01",
 	"eu02",
+	"unknown_default_open_api",
 }
 
 func (v *Region) UnmarshalJSON(src []byte) error {
@@ -44,7 +46,8 @@ func (v *Region) UnmarshalJSON(src []byte) error {
 		}
 	}
 
-	return fmt.Errorf("%+v is not a valid Region", value)
+	*v = REGION_UNKNOWN_DEFAULT_OPEN_API
+	return nil
 }
 
 // NewRegionFromValue returns a pointer to a valid Region
diff --git a/services/vpn/v1beta1api/model_routing_type.go b/services/vpn/v1beta1api/model_routing_type.go
index 11f91bae3..3b9b2af2e 100644
--- a/services/vpn/v1beta1api/model_routing_type.go
+++ b/services/vpn/v1beta1api/model_routing_type.go
@@ -20,9 +20,10 @@ type RoutingType string
 
 // List of RoutingType
 const (
-	ROUTINGTYPE_POLICY_BASED    RoutingType = "POLICY_BASED"
-	ROUTINGTYPE_ROUTE_BASED     RoutingType = "ROUTE_BASED"
-	ROUTINGTYPE_BGP_ROUTE_BASED RoutingType = "BGP_ROUTE_BASED"
+	ROUTINGTYPE_POLICY_BASED             RoutingType = "POLICY_BASED"
+	ROUTINGTYPE_ROUTE_BASED              RoutingType = "ROUTE_BASED"
+	ROUTINGTYPE_BGP_ROUTE_BASED          RoutingType = "BGP_ROUTE_BASED"
+	ROUTINGTYPE_UNKNOWN_DEFAULT_OPEN_API RoutingType = "unknown_default_open_api"
 )
 
 // All allowed values of RoutingType enum
@@ -30,6 +31,7 @@ var AllowedRoutingTypeEnumValues = []RoutingType{
 	"POLICY_BASED",
 	"ROUTE_BASED",
 	"BGP_ROUTE_BASED",
+	"unknown_default_open_api",
 }
 
 func (v *RoutingType) UnmarshalJSON(src []byte) error {
@@ -46,7 +48,8 @@ func (v *RoutingType) UnmarshalJSON(src []byte) error {
 		}
 	}
 
-	return fmt.Errorf("%+v is not a valid RoutingType", value)
+	*v = ROUTINGTYPE_UNKNOWN_DEFAULT_OPEN_API
+	return nil
 }
 
 // NewRoutingTypeFromValue returns a pointer to a valid RoutingType