CVE-2018-13599

Vulnerability

The ResidualValue Ethereum token contract contains an integer overflow vulnerability in its mintToken function [1]. When the owner of the contract calls this function, it updates the caller-supplied recipient's balance by adding a mintedAmount to the existing balance without proper bounds checking [1]. This arithmetic operation can overflow a uint256 value, allowing the owner to set the balance to any arbitrary value, including a value that overflows back to a smaller unintended number [1]. The issue affects the version of the contract as found in the ResidualValue repository (no specific version tag given) [2].

Exploitation

An attacker would first need to be the owner of the ResidualValue contract, as the mintToken function is owner-only [1][2]. The owner simply calls mintToken with a target user's address and a large mintedAmount value. Due to integer overflow, the resulting balanceOf[target] += mintedAmount operation wraps around, enabling the owner to set the balance to any desired value, including extremely high token amounts [1].

Impact

Once the overflow is triggered, the owner can assign any number of tokens to any address [1]. This effectively destroys the token's supply integrity and can lead to the inflation of total supply without limit. Because the contract relies on the mintedAmount being added safely, the owner can mint tokens out of thin air and assign them to any user, enabling theft of value from other holders or manipulation of the token economy [1].

Mitigation

No official fix has been published for the ResidualValue contract [2]. The repository shows the vulnerable code with no subsequent patch [1][2]. Users are advised to treat this token as unmaintained and to avoid acquiring or relying on it. Smart contract developers should use SafeMath library functions (e.g., add(), sub()) to prevent integer overflows in all arithmetic operations [1].