XCM: Deny barrier checks for nested XCMs with specific instructions to be executed on the local chain

cumulus/parachains/runtimes/assets/asset-hub-rococo/src/xcm_config.rs

@@ -51,7 +51,7 @@ use xcm::latest::{prelude::*, ROCOCO_GENESIS_HASH, WESTEND_GENESIS_HASH};
 use xcm_builder::{
 	AccountId32Aliases, AliasChildLocation, AllowExplicitUnpaidExecutionFrom,
 	AllowHrmpNotificationsFromRelayChain, AllowKnownQueryResponses, AllowSubscriptionsFrom,
-	AllowTopLevelPaidExecutionFrom, DenyReserveTransferToRelayChain, DenyThenTry,
+	AllowTopLevelPaidExecutionFrom, DenyRecursively, DenyReserveTransferToRelayChain, DenyThenTry,
 	DescribeAllTerminal, DescribeFamily, EnsureXcmOrigin, FrameTransactionalProcessor,
 	FungibleAdapter, FungiblesAdapter, GlobalConsensusParachainConvertsFor, HashedDescription,
 	IsConcrete, LocalMint, MatchedConvertedConcreteId, NetworkExportTableItem, NoChecking,
@@ -269,7 +269,7 @@ impl Contains<Location> for ParentOrParentsPlurality {
 
 pub type Barrier = TrailingSetTopicAsId<
 	DenyThenTry<
-		DenyReserveTransferToRelayChain,
+		DenyRecursively<DenyReserveTransferToRelayChain>,
 		(
 			TakeWeightCredit,
 			// Expected responses are OK.

cumulus/parachains/runtimes/assets/asset-hub-westend/src/xcm_config.rs

@@ -48,7 +48,7 @@ use xcm::latest::{prelude::*, ROCOCO_GENESIS_HASH, WESTEND_GENESIS_HASH};
 use xcm_builder::{
 	AccountId32Aliases, AliasChildLocation, AllowExplicitUnpaidExecutionFrom,
 	AllowHrmpNotificationsFromRelayChain, AllowKnownQueryResponses, AllowSubscriptionsFrom,
-	AllowTopLevelPaidExecutionFrom, DenyReserveTransferToRelayChain, DenyThenTry,
+	AllowTopLevelPaidExecutionFrom, DenyRecursively, DenyReserveTransferToRelayChain, DenyThenTry,
 	DescribeAllTerminal, DescribeFamily, EnsureXcmOrigin, FrameTransactionalProcessor,
 	FungibleAdapter, FungiblesAdapter, GlobalConsensusParachainConvertsFor, HashedDescription,
 	IsConcrete, LocalMint, MatchedConvertedConcreteId, NetworkExportTableItem, NoChecking,
@@ -281,7 +281,7 @@ impl Contains<Location> for AmbassadorEntities {
 
 pub type Barrier = TrailingSetTopicAsId<
 	DenyThenTry<
-		DenyReserveTransferToRelayChain,
+		DenyRecursively<DenyReserveTransferToRelayChain>,
 		(
 			TakeWeightCredit,
 			// Expected responses are OK.

cumulus/parachains/runtimes/bridge-hubs/bridge-hub-rococo/src/xcm_config.rs

@@ -44,12 +44,12 @@ use xcm::latest::{prelude::*, ROCOCO_GENESIS_HASH};
 use xcm_builder::{
 	AccountId32Aliases, AllowExplicitUnpaidExecutionFrom, AllowHrmpNotificationsFromRelayChain,
 	AllowKnownQueryResponses, AllowSubscriptionsFrom, AllowTopLevelPaidExecutionFrom,
-	DenyReserveTransferToRelayChain, DenyThenTry, DescribeAllTerminal, DescribeFamily,
-	EnsureXcmOrigin, FrameTransactionalProcessor, FungibleAdapter, HandleFee, HashedDescription,
-	IsConcrete, ParentAsSuperuser, ParentIsPreset, RelayChainAsNative, SendXcmFeeToAccount,
-	SiblingParachainAsNative, SiblingParachainConvertsVia, SignedAccountId32AsNative,
-	SignedToAccountId32, SovereignSignedViaLocation, TakeWeightCredit, TrailingSetTopicAsId,
-	UsingComponents, WeightInfoBounds, WithComputedOrigin, WithUniqueTopic,
+	DenyRecursively, DenyReserveTransferToRelayChain, DenyThenTry, DescribeAllTerminal,
+	DescribeFamily, EnsureXcmOrigin, FrameTransactionalProcessor, FungibleAdapter, HandleFee,
+	HashedDescription, IsConcrete, ParentAsSuperuser, ParentIsPreset, RelayChainAsNative,
+	SendXcmFeeToAccount, SiblingParachainAsNative, SiblingParachainConvertsVia,
+	SignedAccountId32AsNative, SignedToAccountId32, SovereignSignedViaLocation, TakeWeightCredit,
+	TrailingSetTopicAsId, UsingComponents, WeightInfoBounds, WithComputedOrigin, WithUniqueTopic,
 };
 use xcm_executor::{
 	traits::{FeeManager, FeeReason, FeeReason::Export},
@@ -131,7 +131,7 @@ impl Contains<Location> for ParentOrParentsPlurality {
 
 pub type Barrier = TrailingSetTopicAsId<
 	DenyThenTry<
-		DenyReserveTransferToRelayChain,
+		DenyRecursively<DenyReserveTransferToRelayChain>,
 		(
 			// Allow local users to buy weight credit.
 			TakeWeightCredit,

cumulus/parachains/runtimes/bridge-hubs/bridge-hub-westend/src/xcm_config.rs

@@ -43,12 +43,12 @@ use xcm::latest::{prelude::*, WESTEND_GENESIS_HASH};
 use xcm_builder::{
 	AccountId32Aliases, AllowExplicitUnpaidExecutionFrom, AllowHrmpNotificationsFromRelayChain,
 	AllowKnownQueryResponses, AllowSubscriptionsFrom, AllowTopLevelPaidExecutionFrom,
-	DenyReserveTransferToRelayChain, DenyThenTry, DescribeAllTerminal, DescribeFamily,
-	EnsureXcmOrigin, FrameTransactionalProcessor, FungibleAdapter, HandleFee, HashedDescription,
-	IsConcrete, ParentAsSuperuser, ParentIsPreset, RelayChainAsNative, SendXcmFeeToAccount,
-	SiblingParachainAsNative, SiblingParachainConvertsVia, SignedAccountId32AsNative,
-	SignedToAccountId32, SovereignSignedViaLocation, TakeWeightCredit, TrailingSetTopicAsId,
-	UsingComponents, WeightInfoBounds, WithComputedOrigin, WithUniqueTopic,
+	DenyRecursively, DenyReserveTransferToRelayChain, DenyThenTry, DescribeAllTerminal,
+	DescribeFamily, EnsureXcmOrigin, FrameTransactionalProcessor, FungibleAdapter, HandleFee,
+	HashedDescription, IsConcrete, ParentAsSuperuser, ParentIsPreset, RelayChainAsNative,
+	SendXcmFeeToAccount, SiblingParachainAsNative, SiblingParachainConvertsVia,
+	SignedAccountId32AsNative, SignedToAccountId32, SovereignSignedViaLocation, TakeWeightCredit,
+	TrailingSetTopicAsId, UsingComponents, WeightInfoBounds, WithComputedOrigin, WithUniqueTopic,
 };
 use xcm_executor::{
 	traits::{FeeManager, FeeReason, FeeReason::Export},
@@ -129,7 +129,7 @@ impl Contains<Location> for ParentOrParentsPlurality {
 
 pub type Barrier = TrailingSetTopicAsId<
 	DenyThenTry<
-		DenyReserveTransferToRelayChain,
+		DenyRecursively<DenyReserveTransferToRelayChain>,
 		(
 			// Allow local users to buy weight credit.
 			TakeWeightCredit,

cumulus/parachains/runtimes/collectives/collectives-westend/src/xcm_config.rs

@@ -37,13 +37,13 @@ use xcm_builder::{
 	AccountId32Aliases, AliasChildLocation, AliasOriginRootUsingFilter,
 	AllowExplicitUnpaidExecutionFrom, AllowHrmpNotificationsFromRelayChain,
 	AllowKnownQueryResponses, AllowSubscriptionsFrom, AllowTopLevelPaidExecutionFrom,
-	DenyReserveTransferToRelayChain, DenyThenTry, DescribeAllTerminal, DescribeFamily,
-	EnsureXcmOrigin, FrameTransactionalProcessor, FungibleAdapter, HashedDescription, IsConcrete,
-	LocatableAssetId, OriginToPluralityVoice, ParentAsSuperuser, ParentIsPreset,
-	RelayChainAsNative, SendXcmFeeToAccount, SiblingParachainAsNative, SiblingParachainConvertsVia,
-	SignedAccountId32AsNative, SignedToAccountId32, SovereignSignedViaLocation, TakeWeightCredit,
-	TrailingSetTopicAsId, UsingComponents, WeightInfoBounds, WithComputedOrigin, WithUniqueTopic,
-	XcmFeeManagerFromComponents,
+	DenyRecursively, DenyReserveTransferToRelayChain, DenyThenTry, DescribeAllTerminal,
+	DescribeFamily, EnsureXcmOrigin, FrameTransactionalProcessor, FungibleAdapter,
+	HashedDescription, IsConcrete, LocatableAssetId, OriginToPluralityVoice, ParentAsSuperuser,
+	ParentIsPreset, RelayChainAsNative, SendXcmFeeToAccount, SiblingParachainAsNative,
+	SiblingParachainConvertsVia, SignedAccountId32AsNative, SignedToAccountId32,
+	SovereignSignedViaLocation, TakeWeightCredit, TrailingSetTopicAsId, UsingComponents,
+	WeightInfoBounds, WithComputedOrigin, WithUniqueTopic, XcmFeeManagerFromComponents,
 };
 use xcm_executor::XcmExecutor;
 
@@ -146,7 +146,7 @@ impl Contains<Location> for LocalPlurality {
 
 pub type Barrier = TrailingSetTopicAsId<
 	DenyThenTry<
-		DenyReserveTransferToRelayChain,
+		DenyRecursively<DenyReserveTransferToRelayChain>,
 		(
 			// Allow local users to buy weight credit.
 			TakeWeightCredit,

cumulus/parachains/runtimes/contracts/contracts-rococo/src/xcm_config.rs

@@ -40,9 +40,9 @@ use xcm::latest::{prelude::*, ROCOCO_GENESIS_HASH};
 use xcm_builder::{
 	AccountId32Aliases, AllowExplicitUnpaidExecutionFrom, AllowHrmpNotificationsFromRelayChain,
 	AllowKnownQueryResponses, AllowSubscriptionsFrom, AllowTopLevelPaidExecutionFrom,
-	DenyReserveTransferToRelayChain, DenyThenTry, DescribeAllTerminal, DescribeFamily,
-	EnsureXcmOrigin, FixedWeightBounds, FrameTransactionalProcessor, FungibleAdapter,
-	HashedDescription, IsConcrete, NativeAsset, ParentAsSuperuser, ParentIsPreset,
+	DenyRecursively, DenyReserveTransferToRelayChain, DenyThenTry, DescribeAllTerminal,
+	DescribeFamily, EnsureXcmOrigin, FixedWeightBounds, FrameTransactionalProcessor,
+	FungibleAdapter, HashedDescription, IsConcrete, NativeAsset, ParentAsSuperuser, ParentIsPreset,
 	RelayChainAsNative, SendXcmFeeToAccount, SiblingParachainAsNative, SiblingParachainConvertsVia,
 	SignedAccountId32AsNative, SignedToAccountId32, SovereignSignedViaLocation, TakeWeightCredit,
 	TrailingSetTopicAsId, UsingComponents, WithComputedOrigin, WithUniqueTopic,
@@ -134,7 +134,7 @@ impl Contains<Location> for ParentOrParentsPlurality {
 
 pub type Barrier = TrailingSetTopicAsId<
 	DenyThenTry<
-		DenyReserveTransferToRelayChain,
+		DenyRecursively<DenyReserveTransferToRelayChain>,
 		(
 			TakeWeightCredit,
 			// Expected responses are OK.

cumulus/parachains/runtimes/coretime/coretime-rococo/src/xcm_config.rs

@@ -41,12 +41,12 @@ use xcm::latest::{prelude::*, ROCOCO_GENESIS_HASH};
 use xcm_builder::{
 	AccountId32Aliases, AllowExplicitUnpaidExecutionFrom, AllowHrmpNotificationsFromRelayChain,
 	AllowKnownQueryResponses, AllowSubscriptionsFrom, AllowTopLevelPaidExecutionFrom,
-	DenyReserveTransferToRelayChain, DenyThenTry, DescribeAllTerminal, DescribeFamily,
-	EnsureXcmOrigin, FrameTransactionalProcessor, FungibleAdapter, HashedDescription, IsConcrete,
-	NonFungibleAdapter, ParentAsSuperuser, ParentIsPreset, RelayChainAsNative, SendXcmFeeToAccount,
-	SiblingParachainAsNative, SiblingParachainConvertsVia, SignedAccountId32AsNative,
-	SignedToAccountId32, SovereignSignedViaLocation, TakeWeightCredit, TrailingSetTopicAsId,
-	UsingComponents, WeightInfoBounds, WithComputedOrigin, WithUniqueTopic,
+	DenyRecursively, DenyReserveTransferToRelayChain, DenyThenTry, DescribeAllTerminal,
+	DescribeFamily, EnsureXcmOrigin, FrameTransactionalProcessor, FungibleAdapter,
+	HashedDescription, IsConcrete, NonFungibleAdapter, ParentAsSuperuser, ParentIsPreset,
+	RelayChainAsNative, SendXcmFeeToAccount, SiblingParachainAsNative, SiblingParachainConvertsVia,
+	SignedAccountId32AsNative, SignedToAccountId32, SovereignSignedViaLocation, TakeWeightCredit,
+	TrailingSetTopicAsId, UsingComponents, WeightInfoBounds, WithComputedOrigin, WithUniqueTopic,
 	XcmFeeManagerFromComponents,
 };
 use xcm_executor::XcmExecutor;
@@ -145,7 +145,7 @@ impl Contains<Location> for ParentOrParentsPlurality {
 
 pub type Barrier = TrailingSetTopicAsId<
 	DenyThenTry<
-		DenyReserveTransferToRelayChain,
+		DenyRecursively<DenyReserveTransferToRelayChain>,
 		(
 			// Allow local users to buy weight credit.
 			TakeWeightCredit,

cumulus/parachains/runtimes/coretime/coretime-westend/src/xcm_config.rs

@@ -42,12 +42,12 @@ use xcm_builder::{
 	AccountId32Aliases, AliasChildLocation, AliasOriginRootUsingFilter,
 	AllowExplicitUnpaidExecutionFrom, AllowHrmpNotificationsFromRelayChain,
 	AllowKnownQueryResponses, AllowSubscriptionsFrom, AllowTopLevelPaidExecutionFrom,
-	DenyReserveTransferToRelayChain, DenyThenTry, DescribeAllTerminal, DescribeFamily,
-	EnsureXcmOrigin, FrameTransactionalProcessor, FungibleAdapter, HashedDescription, IsConcrete,
-	NonFungibleAdapter, ParentAsSuperuser, ParentIsPreset, RelayChainAsNative, SendXcmFeeToAccount,
-	SiblingParachainAsNative, SiblingParachainConvertsVia, SignedAccountId32AsNative,
-	SignedToAccountId32, SovereignSignedViaLocation, TakeWeightCredit, TrailingSetTopicAsId,
-	UsingComponents, WeightInfoBounds, WithComputedOrigin, WithUniqueTopic,
+	DenyRecursively, DenyReserveTransferToRelayChain, DenyThenTry, DescribeAllTerminal,
+	DescribeFamily, EnsureXcmOrigin, FrameTransactionalProcessor, FungibleAdapter,
+	HashedDescription, IsConcrete, NonFungibleAdapter, ParentAsSuperuser, ParentIsPreset,
+	RelayChainAsNative, SendXcmFeeToAccount, SiblingParachainAsNative, SiblingParachainConvertsVia,
+	SignedAccountId32AsNative, SignedToAccountId32, SovereignSignedViaLocation, TakeWeightCredit,
+	TrailingSetTopicAsId, UsingComponents, WeightInfoBounds, WithComputedOrigin, WithUniqueTopic,
 	XcmFeeManagerFromComponents,
 };
 use xcm_executor::XcmExecutor;
@@ -154,7 +154,7 @@ impl Contains<Location> for FellowsPlurality {
 
 pub type Barrier = TrailingSetTopicAsId<
 	DenyThenTry<
-		DenyReserveTransferToRelayChain,
+		DenyRecursively<DenyReserveTransferToRelayChain>,
 		(
 			// Allow local users to buy weight credit.
 			TakeWeightCredit,

cumulus/parachains/runtimes/people/people-rococo/src/xcm_config.rs

@@ -38,10 +38,10 @@ use xcm::latest::{prelude::*, ROCOCO_GENESIS_HASH};
 use xcm_builder::{
 	AccountId32Aliases, AllowExplicitUnpaidExecutionFrom, AllowHrmpNotificationsFromRelayChain,
 	AllowKnownQueryResponses, AllowSubscriptionsFrom, AllowTopLevelPaidExecutionFrom,
-	DenyReserveTransferToRelayChain, DenyThenTry, DescribeAllTerminal, DescribeFamily,
-	DescribeTerminus, EnsureXcmOrigin, FrameTransactionalProcessor, FungibleAdapter,
-	HashedDescription, IsConcrete, ParentAsSuperuser, ParentIsPreset, RelayChainAsNative,
-	SendXcmFeeToAccount, SiblingParachainAsNative, SiblingParachainConvertsVia,
+	DenyRecursively, DenyReserveTransferToRelayChain, DenyThenTry, DescribeAllTerminal,
+	DescribeFamily, DescribeTerminus, EnsureXcmOrigin, FrameTransactionalProcessor,
+	FungibleAdapter, HashedDescription, IsConcrete, ParentAsSuperuser, ParentIsPreset,
+	RelayChainAsNative, SendXcmFeeToAccount, SiblingParachainAsNative, SiblingParachainConvertsVia,
 	SignedAccountId32AsNative, SignedToAccountId32, SovereignSignedViaLocation, TakeWeightCredit,
 	TrailingSetTopicAsId, UsingComponents, WeightInfoBounds, WithComputedOrigin, WithUniqueTopic,
 	XcmFeeManagerFromComponents,
@@ -153,7 +153,7 @@ impl Contains<Location> for ParentOrParentsPlurality {
 
 pub type Barrier = TrailingSetTopicAsId<
 	DenyThenTry<
-		DenyReserveTransferToRelayChain,
+		DenyRecursively<DenyReserveTransferToRelayChain>,
 		(
 			// Allow local users to buy weight credit.
 			TakeWeightCredit,

cumulus/parachains/runtimes/people/people-westend/src/xcm_config.rs

@@ -39,10 +39,10 @@ use xcm_builder::{
 	AccountId32Aliases, AliasChildLocation, AliasOriginRootUsingFilter,
 	AllowExplicitUnpaidExecutionFrom, AllowHrmpNotificationsFromRelayChain,
 	AllowKnownQueryResponses, AllowSubscriptionsFrom, AllowTopLevelPaidExecutionFrom,
-	DenyReserveTransferToRelayChain, DenyThenTry, DescribeAllTerminal, DescribeFamily,
-	DescribeTerminus, EnsureXcmOrigin, FrameTransactionalProcessor, FungibleAdapter,
-	HashedDescription, IsConcrete, ParentAsSuperuser, ParentIsPreset, RelayChainAsNative,
-	SendXcmFeeToAccount, SiblingParachainAsNative, SiblingParachainConvertsVia,
+	DenyRecursively, DenyReserveTransferToRelayChain, DenyThenTry, DescribeAllTerminal,
+	DescribeFamily, DescribeTerminus, EnsureXcmOrigin, FrameTransactionalProcessor,
+	FungibleAdapter, HashedDescription, IsConcrete, ParentAsSuperuser, ParentIsPreset,
+	RelayChainAsNative, SendXcmFeeToAccount, SiblingParachainAsNative, SiblingParachainConvertsVia,
 	SignedAccountId32AsNative, SignedToAccountId32, SovereignSignedViaLocation, TakeWeightCredit,
 	TrailingSetTopicAsId, UsingComponents, WeightInfoBounds, WithComputedOrigin, WithUniqueTopic,
 	XcmFeeManagerFromComponents,
@@ -162,7 +162,7 @@ impl Contains<Location> for FellowsPlurality {
 
 pub type Barrier = TrailingSetTopicAsId<
 	DenyThenTry<
-		DenyReserveTransferToRelayChain,
+		DenyRecursively<DenyReserveTransferToRelayChain>,
 		(
 			// Allow local users to buy weight credit.
 			TakeWeightCredit,

polkadot/xcm/xcm-builder/Cargo.toml

@@ -13,6 +13,7 @@ workspace = true
 
 [dependencies]
 codec = { features = ["derive"], workspace = true }
+environmental = { workspace = true }
 frame-support = { workspace = true }
 frame-system = { workspace = true }
 impl-trait-for-tuples = { workspace = true }
@@ -21,6 +22,7 @@ pallet-asset-conversion = { workspace = true }
 pallet-transaction-payment = { workspace = true }
 scale-info = { features = ["derive"], workspace = true }
 sp-arithmetic = { workspace = true }
+sp-core = { workspace = true }
 sp-io = { workspace = true }
 sp-runtime = { workspace = true }
 sp-weights = { workspace = true }
@@ -39,7 +41,6 @@ polkadot-primitives = { workspace = true, default-features = true }
 polkadot-runtime-parachains = { workspace = true, default-features = true }
 polkadot-test-runtime = { workspace = true }
 primitive-types = { features = ["codec", "num-traits", "scale-info"], workspace = true }
-sp-core = { workspace = true, default-features = true }
 
 [features]
 default = ["std"]
@@ -62,6 +63,7 @@ runtime-benchmarks = [
 ]
 std = [
 	"codec/std",
+	"environmental/std",
 	"frame-support/std",
 	"frame-system/std",
 	"log/std",
@@ -71,6 +73,7 @@ std = [
 	"primitive-types/std",
 	"scale-info/std",
 	"sp-arithmetic/std",
+	"sp-core/std",
 	"sp-io/std",
 	"sp-runtime/std",
 	"sp-weights/std",

polkadot/xcm/xcm-builder/src/barriers.rs

@@ -573,3 +573,96 @@ impl DenyExecution for DenyReserveTransferToRelayChain {
 		Ok(())
 	}
 }
+
+environmental::environmental!(recursion_count: u8);
+
+/// Denies execution if the XCM contains instructions not meant to run on this chain,
+/// first checking at the top-level and then **recursively**.
+///
+/// This barrier only applies to **locally executed** XCM instructions (`SetAppendix`,
+/// `SetErrorHandler`, and `ExecuteWithOrigin`). Remote parts of the XCM are expected to be
+/// validated by the receiving chain's barrier.
+///
+/// Note: Ensures that restricted instructions do not execute on the local chain, enforcing stricter
+/// execution policies while allowing remote chains to enforce their own rules.
+pub struct DenyRecursively<Inner>(PhantomData<Inner>);
+
+impl<Inner: DenyExecution> DenyRecursively<Inner> {
+	/// Recursively applies the deny filter to a nested XCM.
+	///
+	/// Ensures that restricted instructions are blocked at any depth within the XCM.
+	/// Uses a **recursion counter** to prevent stack overflows from deep nesting.
+	fn deny_recursively<RuntimeCall>(
+		origin: &Location,
+		xcm: &mut Xcm<RuntimeCall>,
+		max_weight: Weight,
+		properties: &mut Properties,
+	) -> Result<ControlFlow<()>, ProcessMessageError> {
+		// Initialise recursion counter for this execution context.
+		recursion_count::using_once(&mut 1, || {
+			// Prevent stack overflow by enforcing a recursion depth limit.
+			recursion_count::with(|count| {
+				if *count > xcm_executor::RECURSION_LIMIT {
+					log::debug!(
+                    	target: "xcm::barriers",
+                    	"Recursion limit exceeded (count: {count}), origin: {:?}, xcm: {:?}, max_weight: {:?}, properties: {:?}",
+                    	origin, xcm, max_weight, properties
+                	);
+					return None;
+				}
+				*count = count.saturating_add(1);
+				Some(())
+			}).flatten().ok_or(ProcessMessageError::StackLimitReached)?;
+
+			// Ensure the counter is decremented even if an early return occurs.
+			sp_core::defer! {
+				recursion_count::with(|count| {
+					*count = count.saturating_sub(1);
+				});
+			}
+
+			// Recursively check the nested XCM instructions.
+			Self::deny_execution(origin, xcm.inner_mut(), max_weight, properties)
+		})?;
+
+		Ok(ControlFlow::Continue(()))
+	}
+}
+
+impl<Inner: DenyExecution> DenyExecution for DenyRecursively<Inner> {
+	/// Denies execution of restricted local nested XCM instructions.
+	///
+	/// This checks for `SetAppendix`, `SetErrorHandler`, and `ExecuteWithOrigin` instruction
+	/// applying the deny filter **recursively** to any nested XCMs found.
+	fn deny_execution<RuntimeCall>(
+		origin: &Location,
+		instructions: &mut [Instruction<RuntimeCall>],
+		max_weight: Weight,
+		properties: &mut Properties,
+	) -> Result<(), ProcessMessageError> {
+		// First, check if the top-level message should be denied.
+		Inner::deny_execution(origin, instructions, max_weight, properties).inspect_err(|e| {
+			log::warn!(
+				target: "xcm::barriers",
+				"DenyRecursively::Inner denied execution, origin: {:?}, instructions: {:?}, max_weight: {:?}, properties: {:?}, error: {:?}",
+				origin, instructions, max_weight, properties, e
+			);
+		})?;
+
+		// If the top-level check passes, check nested instructions recursively.
+		instructions.matcher().match_next_inst_while(
+			|_| true,
+			|inst| match inst {
+				SetAppendix(nested_xcm) |
+				SetErrorHandler(nested_xcm) |
+				ExecuteWithOrigin { xcm: nested_xcm, .. } => Self::deny_recursively::<RuntimeCall>(
+					origin, nested_xcm, max_weight, properties,
+				),
+				_ => Ok(ControlFlow::Continue(())),
+			},
+		)?;
+
+		// Permit everything else
+		Ok(())
+	}
+}