CVE-2018-13744

Vulnerability

The mintToken function in the Crowdnext (CNX) Ethereum smart contract contains an integer overflow vulnerability. The contract, as part of the EtherTokens collection, uses a mintToken function that allows the contract owner to mint new tokens to a specified address. The arithmetic operation that updates the total supply and the recipient's balance is performed without a safe math checks, enabling an overflow. Affected versions include the Crowdnext token implementation as found in the EtherTokens/Crowdnext repository [1][2].

Exploitation

An attacker who is the owner of the vulnerable contract can exploit this integer overflow. The owner calls mintToken with a mintedAmount value designed to cause an overflow in the balance of the target address or the total supply. No special network position or additional authentication is required, as the contract owner already has the privilege to invoke this function. The attack does not require user interaction from the target [1].

Impact

Successful exploitation allows the contract owner to set the balance of any arbitrary user to any value (including zero or near-maximum values). This can lead to a complete loss of token value, enable manipulation of token voting or staking mechanisms, or allow the owner to crash other contracts that depend on the token's balance. The core impact is unauthorized manipulation of token balances (integrity loss) [1].

Mitigation

No official patch for the Crowdnext (CNX) token contract has been published in the available references. The contract is part of a community collection of EtherTokens, and users should assume the contract is unmaintained. Use of a safe math library (e.g., OpenZeppelin's SafeMath) in similar token contracts prevents this issue. No workaround exists for the deployed contract other than refusing to use or rely on the CNX token [1][2].