diff --git a/docs/notifications.md b/docs/notifications.md
index 119130ed1..68889780b 100644
--- a/docs/notifications.md
+++ b/docs/notifications.md
@@ -67,11 +67,11 @@ omitted if empty).
 
 Recognized stream names:
  * `block_added`
-   Filter: `primary` as an integer with primary (speaker) node index from
-   ConsensusData and/or `since` field as an integer value with block
-   index starting from which new block notifications will be received and/or
-   `till` field as an integer values containing block index till which new
-   block notifications will be received.
+   Filter: `primary` as an integer with a valid range of 0-255 with 
+   primary (speaker) node index from ConsensusData and/or `since` field as 
+   an integer value with block index starting from which new block 
+   notifications will be received and/or `till` field as an integer values
+   containing block index till which new block notifications will be received.
  * `header_of_added_block`
    Filter: `primary` as an integer with primary (speaker) node index from
    ConsensusData and/or `since` field as an integer value with header
@@ -85,7 +85,8 @@ Recognized stream names:
  * `notification_from_execution`
    Filter: `contract` field containing a string with hex-encoded Uint160 (LE
    representation) and/or `name` field containing a string with execution 
-   notification name.
+   notification name which should be a valid UTF-8 string not longer than 
+   32 bytes.
  * `transaction_executed`
    Filter: `state` field containing `HALT` or `FAULT` string for successful
    and failed executions respectively and/or `container` field containing
diff --git a/pkg/neorpc/filters.go b/pkg/neorpc/filters.go
index 255d94e86..f05cf9343 100644
--- a/pkg/neorpc/filters.go
+++ b/pkg/neorpc/filters.go
@@ -1,8 +1,13 @@
 package neorpc
 
 import (
+	"errors"
+	"fmt"
+
+	"github.com/nspcc-dev/neo-go/pkg/core/interop/runtime"
 	"github.com/nspcc-dev/neo-go/pkg/core/mempoolevent"
 	"github.com/nspcc-dev/neo-go/pkg/util"
+	"github.com/nspcc-dev/neo-go/pkg/vm/vmstate"
 )
 
 type (
@@ -11,7 +16,7 @@ type (
 	// since/till the specified index inclusively). nil value treated as missing
 	// filter.
 	BlockFilter struct {
-		Primary *int    `json:"primary,omitempty"`
+		Primary *byte   `json:"primary,omitempty"`
 		Since   *uint32 `json:"since,omitempty"`
 		Till    *uint32 `json:"till,omitempty"`
 	}
@@ -49,6 +54,16 @@ type (
 	}
 )
 
+// SubscriptionFilter is an interface for all subscription filters.
+type SubscriptionFilter interface {
+	// IsValid checks whether the filter is valid and returns
+	// a specific [ErrInvalidSubscriptionFilter] error if not.
+	IsValid() error
+}
+
+// ErrInvalidSubscriptionFilter is returned when the subscription filter is invalid.
+var ErrInvalidSubscriptionFilter = errors.New("invalid subscription filter")
+
 // Copy creates a deep copy of the BlockFilter. It handles nil BlockFilter correctly.
 func (f *BlockFilter) Copy() *BlockFilter {
 	if f == nil {
@@ -56,7 +71,7 @@ func (f *BlockFilter) Copy() *BlockFilter {
 	}
 	var res = new(BlockFilter)
 	if f.Primary != nil {
-		res.Primary = new(int)
+		res.Primary = new(byte)
 		*res.Primary = *f.Primary
 	}
 	if f.Since != nil {
@@ -70,6 +85,11 @@ func (f *BlockFilter) Copy() *BlockFilter {
 	return res
 }
 
+// IsValid implements SubscriptionFilter interface.
+func (f BlockFilter) IsValid() error {
+	return nil
+}
+
 // Copy creates a deep copy of the TxFilter. It handles nil TxFilter correctly.
 func (f *TxFilter) Copy() *TxFilter {
 	if f == nil {
@@ -87,6 +107,11 @@ func (f *TxFilter) Copy() *TxFilter {
 	return res
 }
 
+// IsValid implements SubscriptionFilter interface.
+func (f TxFilter) IsValid() error {
+	return nil
+}
+
 // Copy creates a deep copy of the NotificationFilter. It handles nil NotificationFilter correctly.
 func (f *NotificationFilter) Copy() *NotificationFilter {
 	if f == nil {
@@ -104,6 +129,14 @@ func (f *NotificationFilter) Copy() *NotificationFilter {
 	return res
 }
 
+// IsValid implements SubscriptionFilter interface.
+func (f NotificationFilter) IsValid() error {
+	if f.Name != nil && len(*f.Name) > runtime.MaxEventNameLen {
+		return fmt.Errorf("%w: NotificationFilter name parameter must be less than %d", ErrInvalidSubscriptionFilter, runtime.MaxEventNameLen)
+	}
+	return nil
+}
+
 // Copy creates a deep copy of the ExecutionFilter. It handles nil ExecutionFilter correctly.
 func (f *ExecutionFilter) Copy() *ExecutionFilter {
 	if f == nil {
@@ -121,6 +154,17 @@ func (f *ExecutionFilter) Copy() *ExecutionFilter {
 	return res
 }
 
+// IsValid implements SubscriptionFilter interface.
+func (f ExecutionFilter) IsValid() error {
+	if f.State != nil {
+		if *f.State != vmstate.Halt.String() && *f.State != vmstate.Fault.String() {
+			return fmt.Errorf("%w: ExecutionFilter state parameter must be either %s or %s", ErrInvalidSubscriptionFilter, vmstate.Halt, vmstate.Fault)
+		}
+	}
+
+	return nil
+}
+
 // Copy creates a deep copy of the NotaryRequestFilter. It handles nil NotaryRequestFilter correctly.
 func (f *NotaryRequestFilter) Copy() *NotaryRequestFilter {
 	if f == nil {
@@ -141,3 +185,8 @@ func (f *NotaryRequestFilter) Copy() *NotaryRequestFilter {
 	}
 	return res
 }
+
+// IsValid implements SubscriptionFilter interface.
+func (f NotaryRequestFilter) IsValid() error {
+	return nil
+}
diff --git a/pkg/neorpc/filters_test.go b/pkg/neorpc/filters_test.go
index 8f725a588..e38591c5d 100644
--- a/pkg/neorpc/filters_test.go
+++ b/pkg/neorpc/filters_test.go
@@ -16,12 +16,12 @@ func TestBlockFilterCopy(t *testing.T) {
 	tf = bf.Copy()
 	require.Equal(t, bf, tf)
 
-	bf.Primary = new(int)
+	bf.Primary = new(byte)
 	*bf.Primary = 42
 
 	tf = bf.Copy()
 	require.Equal(t, bf, tf)
-	*bf.Primary = 100500
+	*bf.Primary = 100
 	require.NotEqual(t, bf, tf)
 
 	bf.Since = new(uint32)
diff --git a/pkg/neorpc/rpcevent/filter.go b/pkg/neorpc/rpcevent/filter.go
index f2be233ad..9b0bd0c69 100644
--- a/pkg/neorpc/rpcevent/filter.go
+++ b/pkg/neorpc/rpcevent/filter.go
@@ -13,7 +13,7 @@ type (
 	// filter notifications.
 	Comparator interface {
 		EventID() neorpc.EventID
-		Filter() any
+		Filter() neorpc.SubscriptionFilter
 	}
 	// Container is an interface required from notification event to be able to
 	// pass filter.
@@ -42,7 +42,7 @@ func Matches(f Comparator, r Container) bool {
 		} else {
 			b = &r.EventPayload().(*block.Block).Header
 		}
-		primaryOk := filt.Primary == nil || *filt.Primary == int(b.PrimaryIndex)
+		primaryOk := filt.Primary == nil || *filt.Primary == b.PrimaryIndex
 		sinceOk := filt.Since == nil || *filt.Since <= b.Index
 		tillOk := filt.Till == nil || b.Index <= *filt.Till
 		return primaryOk && sinceOk && tillOk
diff --git a/pkg/neorpc/rpcevent/filter_test.go b/pkg/neorpc/rpcevent/filter_test.go
index 6d8d33aad..70cfa9225 100644
--- a/pkg/neorpc/rpcevent/filter_test.go
+++ b/pkg/neorpc/rpcevent/filter_test.go
@@ -18,7 +18,7 @@ import (
 type (
 	testComparator struct {
 		id     neorpc.EventID
-		filter any
+		filter neorpc.SubscriptionFilter
 	}
 	testContainer struct {
 		id  neorpc.EventID
@@ -29,7 +29,7 @@ type (
 func (c testComparator) EventID() neorpc.EventID {
 	return c.id
 }
-func (c testComparator) Filter() any {
+func (c testComparator) Filter() neorpc.SubscriptionFilter {
 	return c.filter
 }
 func (c testContainer) EventID() neorpc.EventID {
@@ -40,8 +40,8 @@ func (c testContainer) EventPayload() any {
 }
 
 func TestMatches(t *testing.T) {
-	primary := 1
-	badPrimary := 2
+	primary := byte(1)
+	badPrimary := byte(2)
 	index := uint32(5)
 	badHigherIndex := uint32(6)
 	badLowerIndex := index - 1
diff --git a/pkg/rpcclient/wsclient.go b/pkg/rpcclient/wsclient.go
index 962b26455..9674766da 100644
--- a/pkg/rpcclient/wsclient.go
+++ b/pkg/rpcclient/wsclient.go
@@ -127,7 +127,7 @@ func (r *blockReceiver) EventID() neorpc.EventID {
 }
 
 // Filter implements neorpc.Comparator interface.
-func (r *blockReceiver) Filter() any {
+func (r *blockReceiver) Filter() neorpc.SubscriptionFilter {
 	if r.filter == nil {
 		return nil
 	}
@@ -174,7 +174,7 @@ func (r *headerOfAddedBlockReceiver) EventID() neorpc.EventID {
 }
 
 // Filter implements neorpc.Comparator interface.
-func (r *headerOfAddedBlockReceiver) Filter() any {
+func (r *headerOfAddedBlockReceiver) Filter() neorpc.SubscriptionFilter {
 	if r.filter == nil {
 		return nil
 	}
@@ -220,7 +220,7 @@ func (r *txReceiver) EventID() neorpc.EventID {
 }
 
 // Filter implements neorpc.Comparator interface.
-func (r *txReceiver) Filter() any {
+func (r *txReceiver) Filter() neorpc.SubscriptionFilter {
 	if r.filter == nil {
 		return nil
 	}
@@ -267,7 +267,7 @@ func (r *executionNotificationReceiver) EventID() neorpc.EventID {
 }
 
 // Filter implements neorpc.Comparator interface.
-func (r *executionNotificationReceiver) Filter() any {
+func (r *executionNotificationReceiver) Filter() neorpc.SubscriptionFilter {
 	if r.filter == nil {
 		return nil
 	}
@@ -314,7 +314,7 @@ func (r *executionReceiver) EventID() neorpc.EventID {
 }
 
 // Filter implements neorpc.Comparator interface.
-func (r *executionReceiver) Filter() any {
+func (r *executionReceiver) Filter() neorpc.SubscriptionFilter {
 	if r.filter == nil {
 		return nil
 	}
@@ -361,7 +361,7 @@ func (r *notaryRequestReceiver) EventID() neorpc.EventID {
 }
 
 // Filter implements neorpc.Comparator interface.
-func (r *notaryRequestReceiver) Filter() any {
+func (r *notaryRequestReceiver) Filter() neorpc.SubscriptionFilter {
 	if r.filter == nil {
 		return nil
 	}
@@ -766,6 +766,11 @@ func (c *WSClient) makeWsRequest(r *neorpc.Request) (*neorpc.Response, error) {
 func (c *WSClient) performSubscription(params []any, rcvr notificationReceiver) (string, error) {
 	var resp string
 
+	if flt := rcvr.Filter(); flt != nil {
+		if err := flt.IsValid(); err != nil {
+			return "", err
+		}
+	}
 	if err := c.performRequest("subscribe", params, &resp); err != nil {
 		return "", err
 	}
@@ -872,11 +877,6 @@ func (c *WSClient) ReceiveExecutions(flt *neorpc.ExecutionFilter, rcvr chan<- *s
 	}
 	params := []any{"transaction_executed"}
 	if flt != nil {
-		if flt.State != nil {
-			if *flt.State != "HALT" && *flt.State != "FAULT" {
-				return "", errors.New("bad state parameter")
-			}
-		}
 		flt = flt.Copy()
 		params = append(params, *flt)
 	}
diff --git a/pkg/rpcclient/wsclient_test.go b/pkg/rpcclient/wsclient_test.go
index 8247901ac..693783e79 100644
--- a/pkg/rpcclient/wsclient_test.go
+++ b/pkg/rpcclient/wsclient_test.go
@@ -369,7 +369,20 @@ func TestWSExecutionVMStateCheck(t *testing.T) {
 	require.NoError(t, wsc.Init())
 	filter := "NONE"
 	_, err = wsc.ReceiveExecutions(&neorpc.ExecutionFilter{State: &filter}, make(chan *state.AppExecResult))
-	require.Error(t, err)
+	require.ErrorIs(t, err, neorpc.ErrInvalidSubscriptionFilter)
+	wsc.Close()
+}
+
+func TestWSExecutionNotificationNameCheck(t *testing.T) {
+	// Will answer successfully if request slips through.
+	srv := initTestServer(t, `{"jsonrpc": "2.0", "id": 1, "result": "55aaff00"}`)
+	wsc, err := NewWS(context.TODO(), httpURLtoWS(srv.URL), WSOptions{})
+	require.NoError(t, err)
+	wsc.getNextRequestID = getTestRequestID
+	require.NoError(t, wsc.Init())
+	filter := "notification_from_execution_with_long_name"
+	_, err = wsc.ReceiveExecutionNotifications(&neorpc.NotificationFilter{Name: &filter}, make(chan *state.ContainedNotificationEvent))
+	require.ErrorIs(t, err, neorpc.ErrInvalidSubscriptionFilter)
 	wsc.Close()
 }
 
@@ -381,7 +394,7 @@ func TestWSFilteredSubscriptions(t *testing.T) {
 	}{
 		{"block header primary",
 			func(t *testing.T, wsc *WSClient) {
-				primary := 3
+				primary := byte(3)
 				_, err := wsc.ReceiveHeadersOfAddedBlocks(&neorpc.BlockFilter{Primary: &primary}, make(chan *block.Header))
 				require.NoError(t, err)
 			},
@@ -389,7 +402,7 @@ func TestWSFilteredSubscriptions(t *testing.T) {
 				param := p.Value(1)
 				filt := new(neorpc.BlockFilter)
 				require.NoError(t, json.Unmarshal(param.RawMessage, filt))
-				require.Equal(t, 3, *filt.Primary)
+				require.Equal(t, byte(3), *filt.Primary)
 				require.Equal(t, (*uint32)(nil), filt.Since)
 				require.Equal(t, (*uint32)(nil), filt.Till)
 			},
@@ -404,7 +417,7 @@ func TestWSFilteredSubscriptions(t *testing.T) {
 				param := p.Value(1)
 				filt := new(neorpc.BlockFilter)
 				require.NoError(t, json.Unmarshal(param.RawMessage, filt))
-				require.Equal(t, (*int)(nil), filt.Primary)
+				require.Equal(t, (*byte)(nil), filt.Primary)
 				require.Equal(t, uint32(3), *filt.Since)
 				require.Equal(t, (*uint32)(nil), filt.Till)
 			},
@@ -419,7 +432,7 @@ func TestWSFilteredSubscriptions(t *testing.T) {
 				param := p.Value(1)
 				filt := new(neorpc.BlockFilter)
 				require.NoError(t, json.Unmarshal(param.RawMessage, filt))
-				require.Equal(t, (*int)(nil), filt.Primary)
+				require.Equal(t, (*byte)(nil), filt.Primary)
 				require.Equal(t, (*uint32)(nil), filt.Since)
 				require.Equal(t, (uint32)(3), *filt.Till)
 			},
@@ -428,7 +441,7 @@ func TestWSFilteredSubscriptions(t *testing.T) {
 			func(t *testing.T, wsc *WSClient) {
 				var (
 					since   uint32 = 3
-					primary        = 2
+					primary        = byte(2)
 					till    uint32 = 5
 				)
 				_, err := wsc.ReceiveHeadersOfAddedBlocks(&neorpc.BlockFilter{
@@ -442,14 +455,14 @@ func TestWSFilteredSubscriptions(t *testing.T) {
 				param := p.Value(1)
 				filt := new(neorpc.BlockFilter)
 				require.NoError(t, json.Unmarshal(param.RawMessage, filt))
-				require.Equal(t, 2, *filt.Primary)
+				require.Equal(t, byte(2), *filt.Primary)
 				require.Equal(t, uint32(3), *filt.Since)
 				require.Equal(t, uint32(5), *filt.Till)
 			},
 		},
 		{"blocks primary",
 			func(t *testing.T, wsc *WSClient) {
-				primary := 3
+				primary := byte(3)
 				_, err := wsc.ReceiveBlocks(&neorpc.BlockFilter{Primary: &primary}, make(chan *block.Block))
 				require.NoError(t, err)
 			},
@@ -457,7 +470,7 @@ func TestWSFilteredSubscriptions(t *testing.T) {
 				param := p.Value(1)
 				filt := new(neorpc.BlockFilter)
 				require.NoError(t, json.Unmarshal(param.RawMessage, filt))
-				require.Equal(t, 3, *filt.Primary)
+				require.Equal(t, byte(3), *filt.Primary)
 				require.Equal(t, (*uint32)(nil), filt.Since)
 				require.Equal(t, (*uint32)(nil), filt.Till)
 			},
@@ -472,7 +485,7 @@ func TestWSFilteredSubscriptions(t *testing.T) {
 				param := p.Value(1)
 				filt := new(neorpc.BlockFilter)
 				require.NoError(t, json.Unmarshal(param.RawMessage, filt))
-				require.Equal(t, (*int)(nil), filt.Primary)
+				require.Equal(t, (*byte)(nil), filt.Primary)
 				require.Equal(t, uint32(3), *filt.Since)
 				require.Equal(t, (*uint32)(nil), filt.Till)
 			},
@@ -487,7 +500,7 @@ func TestWSFilteredSubscriptions(t *testing.T) {
 				param := p.Value(1)
 				filt := new(neorpc.BlockFilter)
 				require.NoError(t, json.Unmarshal(param.RawMessage, filt))
-				require.Equal(t, (*int)(nil), filt.Primary)
+				require.Equal(t, (*byte)(nil), filt.Primary)
 				require.Equal(t, (*uint32)(nil), filt.Since)
 				require.Equal(t, (uint32)(3), *filt.Till)
 			},
@@ -496,7 +509,7 @@ func TestWSFilteredSubscriptions(t *testing.T) {
 			func(t *testing.T, wsc *WSClient) {
 				var (
 					since   uint32 = 3
-					primary        = 2
+					primary        = byte(2)
 					till    uint32 = 5
 				)
 				_, err := wsc.ReceiveBlocks(&neorpc.BlockFilter{
@@ -510,7 +523,7 @@ func TestWSFilteredSubscriptions(t *testing.T) {
 				param := p.Value(1)
 				filt := new(neorpc.BlockFilter)
 				require.NoError(t, json.Unmarshal(param.RawMessage, filt))
-				require.Equal(t, 2, *filt.Primary)
+				require.Equal(t, byte(2), *filt.Primary)
 				require.Equal(t, uint32(3), *filt.Since)
 				require.Equal(t, uint32(5), *filt.Till)
 			},
diff --git a/pkg/services/rpcsrv/client_test.go b/pkg/services/rpcsrv/client_test.go
index b77b44b0f..8cdc51689 100644
--- a/pkg/services/rpcsrv/client_test.go
+++ b/pkg/services/rpcsrv/client_test.go
@@ -2113,9 +2113,9 @@ func TestWSClient_SubscriptionsCompat(t *testing.T) {
 	blocks := getTestBlocks(t)
 	bCount := uint32(0)
 
-	getData := func(t *testing.T) (*block.Block, int, util.Uint160, string, string) {
+	getData := func(t *testing.T) (*block.Block, byte, util.Uint160, string, string) {
 		b1 := blocks[bCount]
-		primary := int(b1.PrimaryIndex)
+		primary := b1.PrimaryIndex
 		tx := b1.Transactions[0]
 		sender := tx.Sender()
 		ntfName := "Transfer"
diff --git a/pkg/services/rpcsrv/server.go b/pkg/services/rpcsrv/server.go
index bb30f566d..5c4e2e9f6 100644
--- a/pkg/services/rpcsrv/server.go
+++ b/pkg/services/rpcsrv/server.go
@@ -2729,7 +2729,7 @@ func (s *Server) subscribe(reqParams params.Params, sub *subscriber) (any, *neor
 		return nil, neorpc.WrapErrorWithData(neorpc.ErrInvalidParams, "P2PSigExtensions are disabled")
 	}
 	// Optional filter.
-	var filter any
+	var filter neorpc.SubscriptionFilter
 	if p := reqParams.Value(1); p != nil {
 		param := *p
 		jd := json.NewDecoder(bytes.NewReader(param.RawMessage))
@@ -2754,16 +2754,18 @@ func (s *Server) subscribe(reqParams params.Params, sub *subscriber) (any, *neor
 		case neorpc.ExecutionEventID:
 			flt := new(neorpc.ExecutionFilter)
 			err = jd.Decode(flt)
-			if err == nil && (flt.State == nil || (*flt.State == "HALT" || *flt.State == "FAULT")) {
-				filter = *flt
-			} else if err == nil {
-				err = errors.New("invalid state")
-			}
+			filter = *flt
 		}
 		if err != nil {
 			return nil, neorpc.WrapErrorWithData(neorpc.ErrInvalidParams, err.Error())
 		}
 	}
+	if filter != nil {
+		err = filter.IsValid()
+		if err != nil {
+			return nil, neorpc.WrapErrorWithData(neorpc.ErrInvalidParams, err.Error())
+		}
+	}
 
 	s.subsLock.Lock()
 	var id int
diff --git a/pkg/services/rpcsrv/subscription.go b/pkg/services/rpcsrv/subscription.go
index ad271cae4..9e3b05893 100644
--- a/pkg/services/rpcsrv/subscription.go
+++ b/pkg/services/rpcsrv/subscription.go
@@ -28,7 +28,7 @@ type (
 	// feed stores subscriber's desired event ID with filter.
 	feed struct {
 		event  neorpc.EventID
-		filter any
+		filter neorpc.SubscriptionFilter
 	}
 )
 
@@ -38,7 +38,7 @@ func (f feed) EventID() neorpc.EventID {
 }
 
 // Filter implements neorpc.EventComparator interface and returns notification filter.
-func (f feed) Filter() any {
+func (f feed) Filter() neorpc.SubscriptionFilter {
 	return f.filter
 }
 
diff --git a/pkg/services/rpcsrv/subscription_test.go b/pkg/services/rpcsrv/subscription_test.go
index c3d83eda2..857f3b2d1 100644
--- a/pkg/services/rpcsrv/subscription_test.go
+++ b/pkg/services/rpcsrv/subscription_test.go
@@ -676,3 +676,30 @@ func TestSubscriptionOverflow(t *testing.T) {
 	finishedFlag.CompareAndSwap(false, true)
 	c.Close()
 }
+
+func TestFilteredSubscriptions_InvalidFilter(t *testing.T) {
+	var cases = map[string]struct {
+		params string
+	}{
+		"notification with long name": {
+			params: `["notification_from_execution", {"name":"notification_from_execution_with_long_name"}]`,
+		},
+		"execution with invalid vm state": {
+			params: `["transaction_executed", {"state":"NOTHALT"}]`,
+		},
+	}
+	chain, rpcSrv, c, respMsgs, finishedFlag := initCleanServerAndWSClient(t)
+	defer chain.Close()
+	defer rpcSrv.Shutdown()
+
+	for name, this := range cases {
+		t.Run(name, func(t *testing.T) {
+			resp := callWSGetRaw(t, c, fmt.Sprintf(`{"jsonrpc": "2.0","method": "subscribe","params": %s,"id": 1}`, this.params), respMsgs)
+			require.NotNil(t, resp.Error)
+			require.Nil(t, resp.Result)
+			require.Contains(t, resp.Error.Error(), neorpc.ErrInvalidSubscriptionFilter.Error())
+		})
+	}
+	finishedFlag.CompareAndSwap(false, true)
+	c.Close()
+}