fix: F-2026-18201 | [Dual Defense] Staking Precompile and Vesting Underflow StateDB Balance Enabling Native Mint and Drain

precompiles/common/balance_handler_test.go

@@ -110,6 +110,14 @@ func TestParseAmount(t *testing.T) {
 			},
 			expAmt: uint256.NewInt(5),
 		},
+		{
+			name: "unrelated denom is ignored",
+			maleate: func() sdk.Event {
+				coinStr := sdk.NewCoins(sdk.NewInt64Coin("foobar", 7)).String()
+				return sdk.NewEvent("bank", sdk.NewAttribute(sdk.AttributeKeyAmount, coinStr))
+			},
+			expAmt: uint256.NewInt(0),
+		},
 		{
 			name: "missing amount",
 			maleate: func() sdk.Event {
@@ -186,6 +194,51 @@ func TestAfterBalanceChange(t *testing.T) {
 	require.Equal(t, "3", stateDB.GetBalance(receiver).String())
 }
 
+// TestAfterBalanceChangeSpendMoreThanBalancePanics reproduces the F-2026-18201
+// attack path at the precompile boundary: the EVM state view only tracks
+// SPENDABLE balance, but a vesting account can delegate LOCKED coins through the
+// staking precompile. That emits a coin_spent event for more than the StateDB
+// holds. Before the underflow guard the subtraction wrapped to ~2^256, and
+// x/vm/keeper/statedb.go reconciled the bogus view back to bank by MINTING the
+// difference. It must now hard-fail instead.
+func TestAfterBalanceChangeSpendMoreThanBalancePanics(t *testing.T) {
+	setupBalanceHandlerTest(t)
+
+	storeKey := storetypes.NewKVStoreKey("test")
+	tKey := storetypes.NewTransientStoreKey("test_t")
+	ctx := sdktestutil.DefaultContext(storeKey, tKey)
+
+	stateDB := statedb.New(ctx, mocks.NewEVMKeeper(), statedb.NewEmptyTxConfig())
+
+	_, addrs, err := testutil.GeneratePrivKeyAddressPairs(1)
+	require.NoError(t, err)
+	spenderAcc := addrs[0]
+	spender := common.BytesToAddress(spenderAcc)
+
+	// Spendable balance as seen by the EVM.
+	stateDB.AddBalance(spender, uint256.NewInt(5), tracing.BalanceChangeUnspecified)
+
+	bankKeeper := cmnmocks.NewBankKeeper(t)
+	bankKeeper.Mock.On("BlockedAddr", mock.AnythingOfType("types.AccAddress")).Return(false)
+
+	bh := cmn.NewBalanceHandlerFactory(bankKeeper).NewBalanceHandler()
+	bh.BeforeBalanceChange(ctx)
+
+	// Delegating locked coins spends more than the spendable balance.
+	ctx.EventManager().EmitEvents(sdk.Events{
+		banktypes.NewCoinSpentEvent(spenderAcc, sdk.NewCoins(sdk.NewInt64Coin(evmtypes.GetEVMCoinDenom(), 10))),
+	})
+
+	require.PanicsWithValue(
+		t,
+		"state balance underflow for "+spender.Hex()+": have=5 sub=10",
+		func() { _ = bh.AfterBalanceChange(ctx, stateDB) },
+	)
+
+	// The balance must not have wrapped around to ~2^256.
+	require.Equal(t, "5", stateDB.GetBalance(spender).String())
+}
+
 func TestAfterBalanceChangeErrors(t *testing.T) {
 	setupBalanceHandlerTest(t)
 

precompiles/common/utils.go

@@ -42,8 +42,18 @@ func ParseAmount(event sdk.Event) (*uint256.Int, error) {
 		return nil, fmt.Errorf("failed to parse coins from %q: %w", amountAttr.Value, err)
 	}
 
-	amountBigInt := amountCoins.AmountOf(evmtypes.GetEVMCoinDenom()).BigInt()
-	amount, err := utils.Uint256FromBigInt(evmtypes.ConvertAmountTo18DecimalsBigInt(amountBigInt))
+	baseAmount := amountCoins.AmountOf(evmtypes.GetEVMCoinDenom()).BigInt()
+	extendedAmount := amountCoins.AmountOf(evmtypes.GetEVMCoinExtendedDenom()).BigInt()
+
+	var amountBigInt *big.Int
+	if baseAmount.Sign() > 0 {
+		amountBigInt = evmtypes.ConvertAmountTo18DecimalsBigInt(baseAmount)
+	} else {
+		// The extended denom is already represented in 18 decimals.
+		amountBigInt = extendedAmount
+	}
+
+	amount, err := utils.Uint256FromBigInt(amountBigInt)
 	if err != nil {
 		return nil, fmt.Errorf("failed to convert coin amount to Uint256: %w", err)
 	}

x/vm/statedb/state_object.go

@@ -2,6 +2,7 @@ package statedb
 
 import (
 	"bytes"
+	"fmt"
 	"sort"
 
 	"github.com/ethereum/go-ethereum/common"
@@ -122,7 +123,16 @@ func (s *stateObject) SubBalance(amount *uint256.Int) uint256.Int {
 	if amount.IsZero() {
 		return *(s.Balance())
 	}
-	return s.SetBalance(new(uint256.Int).Sub(s.Balance(), amount))
+	balance := s.Balance()
+	if balance.Lt(amount) {
+		panic(fmt.Sprintf(
+			"state balance underflow for %s: have=%s sub=%s",
+			s.address.Hex(),
+			balance.String(),
+			amount.String(),
+		))
+	}
+	return s.SetBalance(new(uint256.Int).Sub(balance, amount))
 }
 
 // SetBalance updates account balance.

x/vm/statedb/statedb_test.go

@@ -239,8 +239,17 @@ func (suite *StateDBTestSuite) TestDBError() {
 	}
 }
 
+func (suite *StateDBTestSuite) TestSubBalanceUnderflowPanics() {
+	db := statedb.New(sdk.Context{}.WithEventManager(sdk.NewEventManager()), mocks.NewEVMKeeper(), emptyTxConfig)
+	db.AddBalance(address, uint256.NewInt(1), tracing.BalanceChangeUnspecified)
+
+	expectedPanic := fmt.Sprintf("state balance underflow for %s: have=%s sub=%s", address.Hex(), "1", "2")
+	suite.Require().PanicsWithValue(expectedPanic, func() {
+		db.SubBalance(address, uint256.NewInt(2), tracing.BalanceChangeUnspecified)
+	})
+}
+
 func (suite *StateDBTestSuite) TestBalance() {
-	// NOTE: no need to test overflow/underflow, that is guaranteed by evm implementation.
 	testCases := []struct {
 		name       string
 		malleate   func(*statedb.StateDB)