CVE-2018-13665 in BCaaS
Summary
by MITRE
The mintToken function of a smart contract implementation for BCaaS, 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 as CVE-2018-13665 represents a critical integer overflow flaw within the mintToken function of a smart contract designed for a Blockchain as a Service platform. This specific implementation operates on the Ethereum blockchain and manages token distribution through a minting mechanism that allows contract owners to create new tokens. The integer overflow occurs when the mintToken function processes token amounts that exceed the maximum value that can be stored in the designated data type, typically an unsigned integer. When this overflow condition is triggered, the value wraps around to a much smaller number, creating a scenario where the contract's accounting becomes fundamentally corrupted.
The technical exploitation of this vulnerability stems from the lack of proper input validation and overflow checking within the mintToken function. When a contract owner invokes this function with a large token amount, the system fails to verify that the resulting balance would not exceed the maximum integer limit. This oversight creates a path where an attacker with owner privileges can manipulate the token supply mechanism to artificially inflate or deflate user balances. The vulnerability directly maps to CWE-190, which specifically addresses integer overflow and underflow conditions, and can be classified under the broader category of CWE-682, involving computations with incorrect types or values.
The operational impact of this vulnerability extends beyond simple balance manipulation to potentially compromise the entire token economy and user trust within the platform. An attacker with owner access could theoretically set any user's balance to an arbitrary value, including zeroing out balances or creating infinite token supply conditions. This capability undermines the fundamental principles of token economics and could lead to financial loss for users, contract manipulation, and potential system instability. The vulnerability also presents significant risks for DeFi applications that might rely on this token implementation, as it could enable unauthorized minting or manipulation of token holdings that could affect liquidity, price stability, and smart contract interactions.
Mitigation strategies for this vulnerability require immediate implementation of comprehensive input validation and integer overflow protection mechanisms. The smart contract should incorporate explicit bounds checking before any arithmetic operations that could result in overflow conditions, utilizing safe math libraries or custom overflow detection functions. The contract owner should implement proper access controls and consider using multi-signature wallets for critical operations to reduce the risk of unauthorized exploitation. Additionally, regular security audits and formal verification of smart contract code should be conducted to identify similar vulnerabilities before they can be exploited. This vulnerability aligns with ATT&CK technique T1548.001, which involves privilege escalation through manipulation of system processes, and demonstrates how contract-level vulnerabilities can create persistent security risks within decentralized applications. The remediation process must also include thorough testing of edge cases and comprehensive unit tests to ensure that all possible overflow scenarios are properly handled within the token minting mechanism.