CVE-2018-13668

Vulnerability

The mintToken function in the BTPCoin Ethereum smart contract (an ERC-20 token implementation) contains an integer overflow vulnerability [1]. The function allows the contract owner to mint new tokens to an arbitrary address. The overflow occurs because the arithmetic operation balanceOf[target] += mintedAmount is performed without a safe math check, enabling the owner to overflow the target's balance to any desired value, including extremely large or arbitrary amounts [2]. Affected version: all deployments of the BTPCoin contract as available on GitHub [2].

Exploitation

An attacker who is the contract owner can call the mintToken function with a large mintedAmount value. Because Solidity's default integer arithmetic wraps around on overflow (prior to the widespread use of SafeMath), adding a sufficiently large mintedAmount to the target's existing balance can cause the uint256 sum to overflow, resulting in a controlled and unexpected final balance [1][2]. No other authentication or privilege is required beyond owner access; no user interaction is required.

Impact

A successful exploitation allows the contract owner to arbitrarily set the balance of any user address to any value. This can effectively mint an unlimited number of tokens, leading to a total loss of token supply integrity, potential theft of funds via subsequent transfers, and complete devaluation of the token [2].

Mitigation

No fix is publicly available for the specific BTPCoin contract as indicated in the references; the vulnerable code remains unpatched [2]. The recommended mitigation for developers is to use a safe math library (e.g., OpenZeppelin's SafeMath) to prevent integer overflows [1]. Token holders should treat this contract as untrusted and avoid acquiring or using BTPCoin tokens.