apegurus/unsupported-opcodes

<!-- Source: kadenzipfel/smart-contract-vulnerabilities (MIT) -->

Unsupported Opcodes on EVM-Compatible Chains

Preconditions

• Contract is intended for deployment on an EVM-compatible chain other than Ethereum mainnet (zkSync Era, Arbitrum, Optimism, Polygon, BNB Chain, etc.)
• The contract uses opcodes or patterns that are not supported or behave differently on the target chain

Vulnerable Pattern

// PUSH0 opcode: Solidity >=0.8.20 emits PUSH0
// Not supported on all chains — contract fails to deploy
pragma solidity 0.8.20;

contract Token {
    // Compiled bytecode contains PUSH0 — reverts on chains without support
}

// .transfer() on zkSync Era — 2300 gas stipend insufficient
function withdraw() external {
    // transfer() forwards only 2300 gas
    // On zkSync Era, basic operations cost more — this always reverts
    // Gemholic lost 921 ETH to this exact issue
    payable(msg.sender).transfer(amount);
}

// Dynamic create on zkSync Era
function deploy(bytes memory bytecode) external {
    assembly {
        // zkSync requires bytecode known at compile time
        // Runtime create from arbitrary bytecode fails
        let addr := create(0, add(bytecode, 0x20), mload(bytecode))
    }
}

Detection Heuristics

1. Check the Solidity version: if >=0.8.20, verify the target chain supports the PUSH0 opcode
2. Search for .transfer() and .send() — these use a 2300 gas stipend that may be insufficient on chains with different gas cost structures (especially zkSync Era)
3. Search for assembly create / create2 with runtime-supplied bytecode — this fails on zkSync Era
4. Search for selfdestruct — deprecated and non-functional on some chains post-Dencun
5. If the project targets multiple chains, cross-reference all opcodes used against each target chain's compatibility (use evmdiff.com)

False Positives

• Contract is only deployed on Ethereum mainnet
• Solidity version is <0.8.20 (no PUSH0 emitted)
• .call{value: amount}("") is used instead of .transfer() (forwards all available gas)
• The project explicitly documents which chains are supported and tests against them

Remediation

• Use .call{value: amount}("") instead of .transfer() or .send() for ETH transfers
• For multi-chain deployments, compile with Solidity <0.8.20 or use --evm-version paris to avoid PUSH0
• On zkSync Era, use compile-time known bytecode for contract creation
• Test deployments on each target chain before mainnet launch
• Use evmdiff.com to verify opcode compatibility per chain

// Safe ETH transfer for all EVM chains
function withdraw(uint256 amount) external {
    (bool success,) = msg.sender.call{value: amount}("");
    require(success, "transfer failed");
}

// Avoid PUSH0: compile with Paris EVM target
// solc --evm-version paris