CVE-2018-13748 in CarToken
Summary
by MITRE
The mintToken function of a smart contract implementation for CarToken, an Ethereum token, has an integer overflow that allows the owner of the contract to set the balance of an arbitrary user to any value.
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Analysis
by VulDB Data Team • 03/03/2020
The vulnerability identified in CVE-2018-13748 represents a critical integer overflow flaw within the mintToken function of the CarToken smart contract implementation on the Ethereum blockchain. This issue stems from inadequate input validation and arithmetic overflow handling within the contract's code logic, creating a fundamental security weakness that directly impacts the token's integrity and user account balances. The vulnerability specifically affects the token's ability to properly manage and distribute tokens, as it allows unauthorized manipulation of user account balances through a flaw in the minting process.
The technical implementation of this vulnerability manifests through improper handling of integer arithmetic operations within the mintToken function. When the contract attempts to increment token balances, the lack of overflow checks enables attackers to manipulate the arithmetic operations in such a way that balances can be set to arbitrary values. This occurs because the smart contract code fails to validate that the resulting balance after minting would not exceed the maximum value representable by the integer data type. The flaw directly maps to CWE-190, which describes integer overflow conditions that can lead to unexpected behavior and security vulnerabilities in software implementations.
The operational impact of this vulnerability extends far beyond simple balance manipulation, as it fundamentally compromises the token's economic model and user trust within the blockchain ecosystem. An attacker with access to the contract owner privileges can arbitrarily inflate or deflate user balances, potentially creating infinite token supply scenarios or completely zeroing out user accounts. This capability allows for significant financial manipulation and could result in substantial losses for token holders, as the attacker could mint unlimited tokens for themselves while simultaneously manipulating other users' balances to zero or predetermined values. The vulnerability essentially provides a backdoor for unauthorized wealth redistribution within the token economy.
The exploitation of this vulnerability aligns with several ATT&CK techniques including privilege escalation and resource hijacking, as attackers can leverage their control over the mintToken function to gain unauthorized control over token distribution. The attack vector requires the attacker to possess the contract owner privileges, which typically involves having access to the private keys associated with the contract's administrative functions. This vulnerability demonstrates the critical importance of proper input validation and arithmetic overflow protection in smart contract development, as even a single flawed function can compromise the entire token ecosystem.
Mitigation strategies for this vulnerability require immediate implementation of comprehensive input validation and overflow protection mechanisms within the smart contract code. Developers must ensure that all arithmetic operations include proper bounds checking and overflow detection before any balance modifications occur. The recommended approach involves implementing explicit checks to verify that balance additions will not exceed maximum integer limits, along with proper error handling for overflow conditions. Additionally, contract owners should implement multi-signature requirements for administrative functions and conduct thorough security audits of all smart contract components before deployment to prevent similar vulnerabilities from being introduced in future implementations. The fix should also include regular code reviews and automated testing to validate that arithmetic operations behave correctly under all possible input conditions.