CVE-2018-13669 in NCU
Summary
by MITRE
The mintToken function of a smart contract implementation for NCU, 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 • 02/28/2020
The vulnerability identified in CVE-2018-13669 represents a critical integer overflow flaw within the mintToken function of an Ethereum-based smart contract implementing the NCU token. This vulnerability stems from improper input validation and arithmetic handling within the smart contract code, creating a scenario where the contract owner can manipulate user balances arbitrarily. The flaw occurs when the mintToken function processes token minting operations without adequate overflow checks, allowing malicious or authorized manipulation of token supply and user account balances.
The technical implementation of this vulnerability aligns with CWE-190, Integer Overflow or Wraparound, which specifically addresses conditions where integer arithmetic operations produce results that exceed the maximum value representable by the data type. In Ethereum smart contracts, this typically manifests when uint256 variables are incremented beyond their maximum value of 2^256 - 1, causing the value to wrap around to zero or negative values. The mintToken function's failure to validate input parameters and implement proper overflow protection creates an exploitable condition where the contract owner can manipulate balance values through crafted transactions.
The operational impact of this vulnerability extends beyond simple balance manipulation, potentially enabling contract owner privilege escalation and unauthorized token distribution. An attacker with access to the contract owner account can arbitrarily set user balances to extremely high values, effectively creating unlimited tokens or manipulating the token economy. This vulnerability directly impacts the fundamental principles of blockchain security and trustless systems, as it allows central authority control over token distribution that should be governed by predefined smart contract rules. The consequences include potential loss of user funds, disruption of token economics, and complete undermining of the decentralized trust model that smart contracts are designed to provide.
Mitigation strategies for this vulnerability should include implementing comprehensive input validation and overflow protection mechanisms within the smart contract code. The recommended approach involves utilizing safe math libraries such as OpenZeppelin's SafeMath or similar implementations that automatically check for overflow conditions before arithmetic operations. Additionally, contract owners should implement proper access control measures and conduct thorough code audits using automated tools and manual review processes. The vulnerability demonstrates the critical importance of adhering to established security practices in smart contract development, including the implementation of proper integer arithmetic handling, comprehensive testing procedures, and regular security assessments. Organizations should also consider implementing time-based access controls and multi-signature requirements for contract ownership to reduce the risk associated with single points of failure. This vulnerability serves as a prime example of why security-by-design principles must be fundamental to blockchain development practices, aligning with ATT&CK technique T1548.001 for privilege escalation through contract ownership manipulation.