CVE-2018-13776

Vulnerability

The mintToken function in the AppleToken smart contract (an Ethereum token) contains an integer overflow vulnerability [1]. The function is intended to allow the contract owner to mint new tokens, but due to an unchecked arithmetic operation, the owner can cause an overflow that results in setting the balance of an arbitrary user to any desired value [2]. The affected contract is the AppleToken implementation as hosted in the EtherTokens repository [1]. No specific version numbers are provided, but the vulnerability exists in the code as published.

Exploitation

An attacker who is the owner of the AppleToken contract can exploit this vulnerability by calling the mintToken function with a crafted _value parameter. The integer overflow occurs during the addition of the minted amount to the target user's balance, allowing the owner to bypass normal arithmetic constraints and set the balance to any value, including extremely large or small numbers [2]. No special network position or user interaction is required beyond the owner's existing privileges.

Impact

A successful exploit allows the contract owner to arbitrarily manipulate the token balance of any address. This can be used to inflate the total supply, assign tokens to themselves or others, or effectively destroy tokens by setting balances to zero. The impact is a complete loss of token integrity and trust, as the owner can control all token holdings [1][2].

Mitigation

No official fix or patched version of AppleToken has been released. The vulnerability is inherent in the smart contract code, and users are advised to avoid interacting with this token. As of the publication date (2018-07-09), no workaround exists other than not using the contract [1][2].