OffchainLabs · terencechain · Jun 2, 2026 · Jun 2, 2026
diff --git a/beacon-chain/sync/validate_execution_payload_bid.go b/beacon-chain/sync/validate_execution_payload_bid.go
@@ -121,6 +121,14 @@ func (s *Service) validateExecutionPayloadBidGossip(ctx context.Context, pid pee
 	if err := v.VerifyParentBlockRootSeen(s.cfg.chain.InForkchoice); err != nil {
 		return pubsub.ValidationIgnore, err
 	}
+	// [REJECT] bid.slot is greater than the slot of the block with root bid.parent_block_root.
+	parentSlot, err := s.cfg.chain.RecentBlockSlot(parentBlockRoot)
+	if err != nil {
+		return pubsub.ValidationIgnore, err
+	}
+	if err := v.VerifyBidSlotHigherThanParent(parentSlot); err != nil {
+		return pubsub.ValidationReject, err
+	}
 	msg.ValidatorData = signedBid
 	return pubsub.ValidationAccept, nil
 }

diff --git a/beacon-chain/sync/validate_execution_payload_bid_test.go b/beacon-chain/sync/validate_execution_payload_bid_test.go
@@ -19,6 +19,7 @@ import (
 	"github.com/OffchainLabs/prysm/v7/config/params"
 	"github.com/OffchainLabs/prysm/v7/consensus-types/blocks"
 	"github.com/OffchainLabs/prysm/v7/consensus-types/interfaces"
+	"github.com/OffchainLabs/prysm/v7/consensus-types/primitives"
 	"github.com/OffchainLabs/prysm/v7/encoding/bytesutil"
 	ethpb "github.com/OffchainLabs/prysm/v7/proto/prysm/v1alpha1"
 	"github.com/OffchainLabs/prysm/v7/testing/require"
@@ -141,6 +142,12 @@ func TestValidateExecutionPayloadBidGossip_ErrorPathsWithMock(t *testing.T) {
 			result:    pubsub.ValidationReject,
 			wantError: true,
 		},
+		{
+			name:      "slot not higher than parent",
+			verifier:  mockExecutionPayloadBidVerifier{errSlotHigherThanParent: errors.New("slot not higher than parent")},
+			result:    pubsub.ValidationReject,
+			wantError: true,
+		},
 		{
 			name:      "parent hash mismatch",
 			verifier:  mockExecutionPayloadBidVerifier{errParentBlockHash: errors.New("wrong hash")},
@@ -307,6 +314,7 @@ type mockExecutionPayloadBidVerifier struct {
 	errFeeRecipientMismatch error
 	errGasLimitIncompatible error
 	errParentBlockRootSeen  error
+	errSlotHigherThanParent error
 	errParentBlockHash      error
 	errBuilderCanCoverBid   error
 	errSignature            error
@@ -338,6 +346,10 @@ func (m *mockExecutionPayloadBidVerifier) VerifyParentBlockRootSeen(func([32]byt
 	return m.errParentBlockRootSeen
 }
 
+func (m *mockExecutionPayloadBidVerifier) VerifyBidSlotHigherThanParent(primitives.Slot) error {
+	return m.errSlotHigherThanParent
+}
+
 func (m *mockExecutionPayloadBidVerifier) VerifyParentBlockHash(func([32]byte) ([32]byte, error)) error {
 	return m.errParentBlockHash
 }

diff --git a/beacon-chain/verification/execution_payload_bid.go b/beacon-chain/verification/execution_payload_bid.go
@@ -7,6 +7,7 @@ import (
 	"github.com/OffchainLabs/prysm/v7/beacon-chain/core/gloas"
 	"github.com/OffchainLabs/prysm/v7/beacon-chain/state"
 	"github.com/OffchainLabs/prysm/v7/consensus-types/interfaces"
+	"github.com/OffchainLabs/prysm/v7/consensus-types/primitives"
 	"github.com/pkg/errors"
 )
 
@@ -17,6 +18,7 @@ var ExecutionPayloadBidGossipRequirements = []Requirement{
 	RequireBidExecutionPaymentZero,
 	RequireBidFeeRecipientMatches,
 	RequireBidParentBlockRootSeen,
+	RequireBidSlotHigherThanParent,
 	RequireBidParentBlockHashValid,
 	RequireBidGasLimitCompatible,
 	RequireBidBuilderCanCover,
@@ -33,6 +35,7 @@ var (
 	ErrBidFeeRecipientMismatch    = errors.New("fee recipient does not match proposer preferences")
 	ErrBidGasLimitIncompatible    = errors.New("bid gas limit is incompatible with parent and target")
 	ErrBidParentBlockRootNotSeen  = errors.New("parent block root not seen")
+	ErrBidSlotNotHigherThanParent = errors.New("bid slot is not higher than parent block slot")
 	ErrBidParentBlockHashMismatch = errors.New("parent block hash does not match forkchoice")
 	ErrBidBuilderCannotCover      = errors.New("builder cannot cover bid")
 )
@@ -165,6 +168,20 @@ func (v *BidVerifier) VerifyParentBlockRootSeen(parentSeen func([32]byte) bool)
 	return fmt.Errorf("%w: root=%#x", ErrBidParentBlockRootNotSeen, root)
 }
 
+// VerifyBidSlotHigherThanParent verifies the bid slot is greater than the slot of its parent block.
+func (v *BidVerifier) VerifyBidSlotHigherThanParent(parentSlot primitives.Slot) (err error) {
+	defer v.record(RequireBidSlotHigherThanParent, &err)
+
+	bid, err := v.b.Bid()
+	if err != nil {
+		return errors.Wrap(err, "failed to get bid")
+	}
+	if bid.Slot() <= parentSlot {
+		return fmt.Errorf("%w: bid=%d parent=%d", ErrBidSlotNotHigherThanParent, bid.Slot(), parentSlot)
+	}
+	return nil
+}
+
 // VerifyParentBlockHash verifies the parent execution block hash matches forkchoice for the bid parent root.
 func (v *BidVerifier) VerifyParentBlockHash(resolveBlockHash func([32]byte) ([32]byte, error)) (err error) {
 	defer v.record(RequireBidParentBlockHashValid, &err)

diff --git a/beacon-chain/verification/execution_payload_bid_test.go b/beacon-chain/verification/execution_payload_bid_test.go
@@ -138,6 +138,21 @@ func TestBidVerifier_VerifyParentBlockRootSeen(t *testing.T) {
 	require.ErrorIs(t, verifier.VerifyParentBlockRootSeen(func([32]byte) bool { return false }), ErrBidParentBlockRootNotSeen)
 }
 
+func TestBidVerifier_VerifyBidSlotHigherThanParent(t *testing.T) {
+	signed := testSignedExecutionPayloadBid(t, 10)
+	wrapped, err := blocks.WrappedROSignedExecutionPayloadBid(signed)
+	require.NoError(t, err)
+
+	verifier := &BidVerifier{results: newResults(RequireBidSlotHigherThanParent), b: wrapped}
+	require.NoError(t, verifier.VerifyBidSlotHigherThanParent(9))
+
+	verifier = &BidVerifier{results: newResults(RequireBidSlotHigherThanParent), b: wrapped}
+	require.ErrorIs(t, verifier.VerifyBidSlotHigherThanParent(10), ErrBidSlotNotHigherThanParent)
+
+	verifier = &BidVerifier{results: newResults(RequireBidSlotHigherThanParent), b: wrapped}
+	require.ErrorIs(t, verifier.VerifyBidSlotHigherThanParent(11), ErrBidSlotNotHigherThanParent)
+}
+
 func TestBidVerifier_VerifyParentBlockHash(t *testing.T) {
 	signed := testSignedExecutionPayloadBid(t, 1)
 	wrapped, err := blocks.WrappedROSignedExecutionPayloadBid(signed)

diff --git a/beacon-chain/verification/interface.go b/beacon-chain/verification/interface.go
@@ -8,6 +8,7 @@ import (
 	"github.com/OffchainLabs/prysm/v7/consensus-types/blocks"
 	"github.com/OffchainLabs/prysm/v7/consensus-types/interfaces"
 	payloadattestation "github.com/OffchainLabs/prysm/v7/consensus-types/payload-attestation"
+	"github.com/OffchainLabs/prysm/v7/consensus-types/primitives"
 	ethpb "github.com/OffchainLabs/prysm/v7/proto/prysm/v1alpha1"
 )
 
@@ -103,6 +104,7 @@ type ExecutionPayloadBidVerifier interface {
 	VerifyExecutionPaymentZero() error
 	VerifyFeeRecipientMatches([]byte) error
 	VerifyParentBlockRootSeen(func([32]byte) bool) error
+	VerifyBidSlotHigherThanParent(parentSlot primitives.Slot) error
 	VerifyParentBlockHash(func([32]byte) ([32]byte, error)) error
 	VerifyGasLimitTargetCompatible(parentGasLimit, targetGasLimit uint64) error
 	VerifyBuilderCanCoverBid(state.ReadOnlyBeaconState) error

diff --git a/beacon-chain/verification/requirements.go b/beacon-chain/verification/requirements.go
@@ -45,6 +45,7 @@ const (
 	RequireBidFeeRecipientMatches
 	RequireBidGasLimitCompatible
 	RequireBidParentBlockRootSeen
+	RequireBidSlotHigherThanParent
 	RequireBidParentBlockHashValid
 	RequireBidBuilderCanCover
 	RequireBidSignatureValid

diff --git a/beacon-chain/verification/result.go b/beacon-chain/verification/result.go
@@ -79,6 +79,8 @@ func (r Requirement) String() string {
 		return "RequireBidGasLimitCompatible"
 	case RequireBidParentBlockRootSeen:
 		return "RequireBidParentBlockRootSeen"
+	case RequireBidSlotHigherThanParent:
+		return "RequireBidSlotHigherThanParent"
 	case RequireBidParentBlockHashValid:
 		return "RequireBidParentBlockHashValid"
 	case RequireBidBuilderCanCover:

diff --git a/changelog/terence_reject-bid-lower-slot-than-parent.md b/changelog/terence_reject-bid-lower-slot-than-parent.md
@@ -0,0 +1,3 @@
+### Added
+
+- Reject gossiped execution payload bids whose slot is not greater than the slot of their parent block.
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1,3 @@
		### Added

		- Reject gossiped execution payload bids whose slot is not greater than the slot of their parent block.