diff --git a/sei-tendermint/internal/consensus/memory_limit_test.go b/sei-tendermint/internal/consensus/memory_limit_test.go
index 61e193d8dd..935ee4ec6b 100644
--- a/sei-tendermint/internal/consensus/memory_limit_test.go
+++ b/sei-tendermint/internal/consensus/memory_limit_test.go
@@ -48,6 +48,7 @@ func TestPeerStateMemoryLimits(t *testing.T) {
 					BlockID:   blockID,
 					Timestamp: time.Now(),
 					Signature: []byte("test-signature"),
+					Header:    plausibleTestHeader,
 				}
 				ps.SetHasProposal(proposal)
 				if tc.expectError {
diff --git a/sei-tendermint/internal/consensus/peer_state_test.go b/sei-tendermint/internal/consensus/peer_state_test.go
index 1eeeee6833..7433a72b9b 100644
--- a/sei-tendermint/internal/consensus/peer_state_test.go
+++ b/sei-tendermint/internal/consensus/peer_state_test.go
@@ -5,6 +5,7 @@ import (
 	"time"
 
 	"github.com/stretchr/testify/require"
+	"github.com/tendermint/tendermint/version"
 
 	"github.com/tendermint/tendermint/crypto"
 	"github.com/tendermint/tendermint/libs/log"
@@ -12,6 +13,14 @@ import (
 	"github.com/tendermint/tendermint/types"
 )
 
+var plausibleTestHeader = types.Header{
+	Version: version.Consensus{
+		Block: version.BlockProtocol,
+	},
+	Height:          1,
+	ProposerAddress: make(types.Address, 20),
+}
+
 func peerStateSetup(h, r, v int) *PeerState {
 	ps := NewPeerState(log.NewNopLogger(), "testPeerState")
 	ps.PRS.Height = int64(h)
@@ -122,6 +131,7 @@ func TestSetHasProposal(t *testing.T) {
 				Hash:  make([]byte, crypto.HashSize),
 			},
 		},
+		Header: plausibleTestHeader,
 		// Missing signature
 	}
 	ps.SetHasProposal(invalidProposal)
@@ -142,6 +152,7 @@ func TestSetHasProposal(t *testing.T) {
 				Hash:  crypto.CRandBytes(crypto.HashSize),
 			},
 		},
+		Header:    plausibleTestHeader,
 		Signature: []byte("signature"),
 	}
 	ps3.SetHasProposal(tooLargeTotalProposal)
@@ -160,6 +171,7 @@ func TestSetHasProposal(t *testing.T) {
 				Hash:  crypto.CRandBytes(crypto.HashSize),
 			},
 		},
+		Header:    plausibleTestHeader,
 		Signature: []byte("signature"),
 	}
 	ps.SetHasProposal(validProposal)
@@ -179,6 +191,7 @@ func TestSetHasProposal(t *testing.T) {
 				Hash:  crypto.CRandBytes(crypto.HashSize),
 			},
 		},
+		Header:    plausibleTestHeader,
 		Signature: []byte("signature"),
 	}
 	ps2.SetHasProposal(differentProposal)
@@ -235,6 +248,7 @@ func TestSetHasProposalMemoryLimit(t *testing.T) {
 
 			// Set up proposal with test case total
 			proposal.BlockID.PartSetHeader.Total = tc.total
+			proposal.Header = plausibleTestHeader // Use a plausible header
 
 			// Try to set the proposal
 			ps.SetHasProposal(proposal)
@@ -424,6 +438,7 @@ func TestSetHasProposalEdgeCases(t *testing.T) {
 				},
 				Timestamp: time.Now(),
 				Signature: []byte("test-signature"),
+				Header:    plausibleTestHeader,
 			},
 			expectProposal: true, // Should be set
 			expectPanic:    false,
diff --git a/sei-tendermint/internal/consensus/reactor_test.go b/sei-tendermint/internal/consensus/reactor_test.go
index 83ab03aea3..4a4faa4f08 100644
--- a/sei-tendermint/internal/consensus/reactor_test.go
+++ b/sei-tendermint/internal/consensus/reactor_test.go
@@ -842,6 +842,7 @@ func TestReactorMemoryLimitCoverage(t *testing.T) {
 			},
 		},
 		Timestamp: time.Now(),
+		Header:    plausibleTestHeader,
 		Signature: []byte("test-signature"),
 	}
 
diff --git a/sei-tendermint/internal/consensus/state_test.go b/sei-tendermint/internal/consensus/state_test.go
index 54b4135019..c4b118fe9b 100644
--- a/sei-tendermint/internal/consensus/state_test.go
+++ b/sei-tendermint/internal/consensus/state_test.go
@@ -2495,8 +2495,22 @@ func TestGossipTransactionKeyOnlyConfig(t *testing.T) {
 	proposalMsg := ProposalMessage{&proposal}
 	peerID, err := types.NewNodeID("AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA")
 	startTestRound(ctx, cs1, height, round)
-	cs1.handleMsg(ctx, msgInfo{&proposalMsg, peerID, time.Now()}, false)
+
+	// Assert invalid proposal is ignored.
+	invalidProposal := proposal
+	invalidProposal.Height = -3
+	cs1.handleMsg(ctx, msgInfo{&ProposalMessage{&invalidProposal}, peerID, time.Now()}, false)
 	rs := cs1.GetRoundState()
+	require.Nil(t, rs.Proposal)
+	require.Nil(t, rs.ProposalBlock)
+	require.Zero(t, rs.ProposalBlockParts.Total())
+
+	// Now assert that a valid proposal is processed correctly.
+	cs1.handleMsg(ctx, msgInfo{&proposalMsg, peerID, time.Now()}, false)
+
+	// GetRoundStates returns a snapshot of the current state. Therefore, we need to
+	// get it again after processing the proposal message.
+	rs = cs1.GetRoundState()
 	// Proposal, ProposalBlock and ProposalBlockParts sohuld be set since gossip-tx-key is true
 	if rs.Proposal == nil {
 		t.Error("rs.Proposal should be set")
diff --git a/sei-tendermint/types/block.go b/sei-tendermint/types/block.go
index 4938de5374..ab32045250 100644
--- a/sei-tendermint/types/block.go
+++ b/sei-tendermint/types/block.go
@@ -37,6 +37,11 @@ const (
 	// Uvarint length of Data.Txs:          4 bytes
 	// Data.Txs field:                      1 byte
 	MaxOverheadForBlock int64 = 11
+
+	// MaxCommitSignatures is the maximum number of signatures in a commit. The max
+	// value is picked relative to the current number of validators and may need to
+	// be increased in the future as the network grows.
+	MaxCommitSignatures = 128
 )
 
 // Block defines the atomic unit of a Tendermint blockchain.
@@ -89,12 +94,7 @@ func (b *Block) ValidateBasic() error {
 		return fmt.Errorf("wrong Header.DataHash. Expected %X, got %X. Len of txs %d", w, g, len(b.Data.Txs))
 	}
 
-	// NOTE: b.Evidence may be nil, but we're just looping.
-	for i, ev := range b.Evidence {
-		if err := ev.ValidateBasic(); err != nil {
-			return fmt.Errorf("invalid evidence (#%d): %v", i, err)
-		}
-	}
+	// Evidence is validated as part of proto decoding. See EvidenceList.FromProto.
 
 	if w, g := b.Evidence.Hash(), b.EvidenceHash; !bytes.Equal(w, g) {
 		return fmt.Errorf("wrong Header.EvidenceHash. Expected %X, got %X", w, g)
@@ -821,6 +821,9 @@ func (commit *Commit) Size() int {
 // ValidateBasic performs basic validation that doesn't involve state data.
 // Does not actually check the cryptographic signatures.
 func (commit *Commit) ValidateBasic() error {
+	if commit == nil {
+		return nil
+	}
 	if commit.Height < 0 {
 		return errors.New("negative Height")
 	}
@@ -926,6 +929,10 @@ func CommitFromProto(cp *tmproto.Commit) (*Commit, error) {
 		return nil, err
 	}
 
+	if len(cp.Signatures) > MaxCommitSignatures {
+		return nil, fmt.Errorf("too many signatures in commit: %d (max: %d)", len(cp.Signatures), MaxCommitSignatures)
+	}
+
 	sigs := make([]CommitSig, len(cp.Signatures))
 	for i := range cp.Signatures {
 		if err := sigs[i].FromProto(cp.Signatures[i]); err != nil {
diff --git a/sei-tendermint/types/block_meta.go b/sei-tendermint/types/block_meta.go
index b35afd3457..01687767a2 100644
--- a/sei-tendermint/types/block_meta.go
+++ b/sei-tendermint/types/block_meta.go
@@ -67,9 +67,15 @@ func BlockMetaFromProto(pb *tmproto.BlockMeta) (*BlockMeta, error) {
 
 // ValidateBasic performs basic validation.
 func (bm *BlockMeta) ValidateBasic() error {
+	if bm == nil {
+		return errors.New("nil BlockMeta")
+	}
 	if err := bm.BlockID.ValidateBasic(); err != nil {
 		return err
 	}
+	if err := bm.Header.ValidateBasic(); err != nil {
+		return err
+	}
 	if !bytes.Equal(bm.BlockID.Hash, bm.Header.Hash()) {
 		return fmt.Errorf("expected BlockID#Hash and Header#Hash to be the same, got %X != %X",
 			bm.BlockID.Hash, bm.Header.Hash())
diff --git a/sei-tendermint/types/evidence.go b/sei-tendermint/types/evidence.go
index 83cb4b391e..83c41d16a5 100644
--- a/sei-tendermint/types/evidence.go
+++ b/sei-tendermint/types/evidence.go
@@ -656,7 +656,7 @@ func (evl *EvidenceList) FromProto(eviList *tmproto.EvidenceList) error {
 		eviBzs[i] = evi
 	}
 	*evl = eviBzs
-	return nil
+	return evl.ValidateBasic()
 }
 
 // ToProto converts EvidenceList to protobuf
@@ -745,6 +745,18 @@ func (evl EvidenceList) ToABCI() []abci.Misbehavior {
 	return el
 }
 
+func (evl EvidenceList) ValidateBasic() error {
+	for at, evidence := range evl {
+		if evidence == nil {
+			return fmt.Errorf("nil evidence in evidence list at index %d", at)
+		}
+		if err := evidence.ValidateBasic(); err != nil {
+			return fmt.Errorf("invalid evidence at index %d: %w", at, err)
+		}
+	}
+	return nil
+}
+
 //------------------------------------------ PROTO --------------------------------------
 
 // EvidenceToProto is a generalized function for encoding evidence that conforms to the
diff --git a/sei-tendermint/types/mempool.go b/sei-tendermint/types/mempool.go
index a3a0c831eb..b1dedcbec7 100644
--- a/sei-tendermint/types/mempool.go
+++ b/sei-tendermint/types/mempool.go
@@ -35,6 +35,9 @@ func TxKeyFromProto(dp *tmproto.TxKey) (TxKey, error) {
 	if dp == nil {
 		return TxKey{}, errors.New("nil data")
 	}
+	if len(dp.TxKey) != sha256.Size {
+		return TxKey{}, fmt.Errorf("invalid tx key length: %d, expected: %d", len(dp.TxKey), sha256.Size)
+	}
 	var txBzs [sha256.Size]byte
 	for i := range dp.TxKey {
 		txBzs[i] = dp.TxKey[i]
@@ -44,6 +47,9 @@ func TxKeyFromProto(dp *tmproto.TxKey) (TxKey, error) {
 }
 
 func TxKeysListFromProto(dps []*tmproto.TxKey) ([]TxKey, error) {
+	if len(dps) > maxTxKeysPerProposal {
+		return nil, fmt.Errorf("too many tx keys in proposal: %d, max: %d", len(dps), maxTxKeysPerProposal)
+	}
 	var txKeys []TxKey
 	for _, txKey := range dps {
 		txKey, err := TxKeyFromProto(txKey)
diff --git a/sei-tendermint/types/node_info.go b/sei-tendermint/types/node_info.go
index 3c7758b672..af64bccb8f 100644
--- a/sei-tendermint/types/node_info.go
+++ b/sei-tendermint/types/node_info.go
@@ -229,7 +229,7 @@ func NodeInfoFromProto(pb *tmp2p.NodeInfo) (NodeInfo, error) {
 		},
 	}
 
-	return dni, nil
+	return dni, dni.Validate()
 }
 
 // ParseAddressString reads an address string, and returns the IP
diff --git a/sei-tendermint/types/proposal.go b/sei-tendermint/types/proposal.go
index b8d4d27a05..bbed73f8d6 100644
--- a/sei-tendermint/types/proposal.go
+++ b/sei-tendermint/types/proposal.go
@@ -3,15 +3,50 @@ package types
 import (
 	"errors"
 	"fmt"
+	"math"
 	"math/bits"
+	"os"
+	"strconv"
 	"time"
 
+	"github.com/tendermint/tendermint/crypto"
 	"github.com/tendermint/tendermint/internal/libs/protoio"
 	tmbytes "github.com/tendermint/tendermint/libs/bytes"
 	tmtime "github.com/tendermint/tendermint/libs/time"
 	tmproto "github.com/tendermint/tendermint/proto/tendermint/types"
 )
 
+// maxTxKeysPerProposal is the maximum number of transaction keys that can be
+// included in a proposal. The limit is determined such that the proposal should
+// hit the gas limit before ever reaching the max transaction keys in order to
+// cap the maximum.
+//
+// By default, we set this to 1,000 which should be reasonable for most use
+// cases. However, this can be overridden by setting the
+// SEI_TENDERMINT_MAX_TX_KEYS_PER_PROPOSAL environment variable to a positive
+// integer value for load testing purposes.
+var maxTxKeysPerProposal int
+
+func init() {
+	const defaultMaxTxKeysPerProposal = 1_000
+	if value, found := os.LookupEnv("SEI_TENDERMINT_MAX_TX_KEYS_PER_PROPOSAL"); found {
+		maxTxKeys, err := strconv.ParseInt(value, 10, 64)
+		if err != nil {
+			panic(fmt.Sprintf("Failed to parse SEI_TENDERMINT_MAX_TX_KEYS_PER_PROPOSAL %s: %v", value, err))
+		}
+		if maxTxKeys <= 0 {
+			panic(fmt.Sprintf("SEI_TENDERMINT_MAX_TX_KEYS_PER_PROPOSAL must be a positive integer, got %d", maxTxKeys))
+		}
+		if maxTxKeys > math.MaxInt {
+			panic(fmt.Sprintf("SEI_TENDERMINT_MAX_TX_KEYS_PER_PROPOSAL must be less than or equal to %d, got %d", math.MaxInt, maxTxKeys))
+		}
+		maxTxKeysPerProposal = int(maxTxKeys)
+		fmt.Printf("Using custom maxTxKeysPerProposal: %d\n", maxTxKeysPerProposal)
+	} else {
+		maxTxKeysPerProposal = defaultMaxTxKeysPerProposal
+	}
+}
+
 var (
 	ErrInvalidBlockPartSignature = errors.New("error invalid block part signature")
 	ErrInvalidBlockPartHash      = errors.New("error invalid block part hash")
@@ -87,6 +122,28 @@ func (p *Proposal) ValidateBasic() error {
 	if len(p.Signature) > MaxSignatureSize {
 		return fmt.Errorf("signature is too big (max: %d)", MaxSignatureSize)
 	}
+
+	if err := p.LastCommit.ValidateBasic(); err != nil {
+		return fmt.Errorf("invalid LastCommit: %w", err)
+	}
+
+	// Evidence is validated as part of proto decoding. See EvidenceList.FromProto.
+
+	if err := p.Header.ValidateBasic(); err != nil {
+		return fmt.Errorf("invalid Header: %w", err)
+	}
+
+	if len(p.TxKeys) > maxTxKeysPerProposal {
+		return fmt.Errorf("invalid number of TxKeys: must be at most %d, got %d", maxTxKeysPerProposal, len(p.TxKeys))
+	}
+
+	if len(p.ProposerAddress) != crypto.AddressSize {
+		return fmt.Errorf(
+			"invalid ProposerAddress length; got: %d, expected: %d",
+			len(p.ProposerAddress), crypto.AddressSize,
+		)
+	}
+
 	return nil
 }
 
@@ -228,9 +285,14 @@ func ProposalFromProto(pp *tmproto.Proposal) (*Proposal, error) {
 	}
 	p.Header = header
 	lastCommit, err := CommitFromProto(pp.LastCommit)
+	if err != nil {
+		return nil, fmt.Errorf("failed to instantiate last commit: %w", err)
+	}
 	p.LastCommit = lastCommit
 	eviD := new(EvidenceList)
-	eviD.FromProto(pp.Evidence)
+	if err := eviD.FromProto(pp.Evidence); err != nil {
+		return nil, fmt.Errorf("faield to instantiate evidence list: %w", err)
+	}
 	p.Evidence = *eviD
 	p.ProposerAddress = pp.ProposerAddress
 
diff --git a/sei-tendermint/types/proposal_test.go b/sei-tendermint/types/proposal_test.go
index 16f1ec9b8a..24ee3e24de 100644
--- a/sei-tendermint/types/proposal_test.go
+++ b/sei-tendermint/types/proposal_test.go
@@ -18,6 +18,8 @@ import (
 	tmproto "github.com/tendermint/tendermint/proto/tendermint/types"
 )
 
+var plausibleTestAddress = crypto.Address(make([]byte, crypto.AddressSize))
+
 func generateHeader() Header {
 	return Header{
 		Version: version.Consensus{Block: version.BlockProtocol},
@@ -182,6 +184,10 @@ func TestProposalValidateBasic(t *testing.T) {
 		{"Too big Signature", func(p *Proposal) {
 			p.Signature = make([]byte, MaxSignatureSize+1)
 		}, true},
+		{"Invalid LastCommit", func(p *Proposal) { p.LastCommit = &Commit{Height: -1} }, true},
+		{"Invalid EvidenceList", func(p *Proposal) { p.Evidence = []Evidence{nil} }, true},
+		{"Invalid Header", func(p *Proposal) { p.Header = Header{ChainID: string(make([]byte, 100))} }, true},
+		{"Too many TxKeys", func(p *Proposal) { p.TxKeys = make([]TxKey, maxTxKeysPerProposal+1) }, true},
 	}
 	blockID := makeBlockID(crypto.Checksum([]byte("blockhash")), math.MaxInt32, crypto.Checksum([]byte("partshash")))
 
@@ -208,9 +214,9 @@ func TestProposalValidateBasic(t *testing.T) {
 
 func TestProposalProtoBuf(t *testing.T) {
 	var txKeys []TxKey
-	proposal := NewProposal(1, 2, 3, makeBlockID([]byte("hash"), 2, []byte("part_set_hash")), tmtime.Now(), txKeys, generateHeader(), &Commit{Signatures: []CommitSig{}}, EvidenceList{}, crypto.Address("testaddr"))
+	proposal := NewProposal(1, 2, 3, makeBlockID([]byte("hash"), 2, []byte("part_set_hash")), tmtime.Now(), txKeys, generateHeader(), &Commit{Signatures: []CommitSig{}}, EvidenceList{}, plausibleTestAddress)
 	proposal.Signature = []byte("sig")
-	proposal2 := NewProposal(1, 2, 3, BlockID{}, tmtime.Now(), txKeys, generateHeader(), &Commit{Signatures: []CommitSig{}}, EvidenceList{}, crypto.Address("testaddr"))
+	proposal2 := NewProposal(1, 2, 3, BlockID{}, tmtime.Now(), txKeys, generateHeader(), &Commit{Signatures: []CommitSig{}}, EvidenceList{}, plausibleTestAddress)
 
 	testCases := []struct {
 		msg     string
diff --git a/sei-tendermint/types/validator.go b/sei-tendermint/types/validator.go
index b542037f20..5ffe1b0891 100644
--- a/sei-tendermint/types/validator.go
+++ b/sei-tendermint/types/validator.go
@@ -209,7 +209,7 @@ func ValidatorFromProto(vp *tmproto.Validator) (*Validator, error) {
 	v.VotingPower = vp.GetVotingPower()
 	v.ProposerPriority = vp.GetProposerPriority()
 
-	return v, nil
+	return v, v.ValidateBasic()
 }
 
 //----------------------------------------
diff --git a/sei-tendermint/types/vote.go b/sei-tendermint/types/vote.go
index 40f829182d..e759e4c029 100644
--- a/sei-tendermint/types/vote.go
+++ b/sei-tendermint/types/vote.go
@@ -68,7 +68,7 @@ func VoteFromProto(pv *tmproto.Vote) (*Vote, error) {
 		return nil, err
 	}
 
-	return &Vote{
+	v := &Vote{
 		Type:             pv.Type,
 		Height:           pv.Height,
 		Round:            pv.Round,
@@ -77,7 +77,8 @@ func VoteFromProto(pv *tmproto.Vote) (*Vote, error) {
 		ValidatorAddress: pv.ValidatorAddress,
 		ValidatorIndex:   pv.ValidatorIndex,
 		Signature:        pv.Signature,
-	}, nil
+	}
+	return v, v.ValidateBasic()
 }
 
 // CommitSig converts the Vote to a CommitSig.
diff --git a/sei-tendermint/types/vote_test.go b/sei-tendermint/types/vote_test.go
index 3ac651ce35..4d46b8b598 100644
--- a/sei-tendermint/types/vote_test.go
+++ b/sei-tendermint/types/vote_test.go
@@ -301,7 +301,7 @@ func TestVoteProtobuf(t *testing.T) {
 		passesValidateBasic bool
 	}{
 		{"success", vote, true, true},
-		{"fail vote validate basic", &Vote{}, true, false},
+		{"fail vote validate basic", &Vote{}, false, false},
 	}
 	for _, tc := range testCases {
 		protoProposal := tc.vote.ToProto()