CVE-2018-13674 in ComBillAdvancedToken
Summary
by MITRE
The mintToken function of a smart contract implementation for ComBillAdvancedToken, 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-2018-13674 represents a critical integer overflow flaw within the mintToken function of the ComBillAdvancedToken smart contract deployed on the Ethereum blockchain. This vulnerability stems from improper input validation and arithmetic handling within the contract's code implementation, specifically affecting the token's minting mechanism that allows contract owners to create new tokens. The flaw manifests when the mintToken function processes token minting operations without adequate overflow checking, creating a scenario where mathematical operations can exceed the maximum value that can be represented by the underlying data type, leading to unexpected behavior in the token balance calculations.
The technical nature of this vulnerability aligns with CWE-190, which categorizes integer overflow conditions as a fundamental weakness in software systems where arithmetic operations exceed the bounds of the data type used to store results. In the context of Ethereum smart contracts, this vulnerability exposes the contract to manipulation through controlled arithmetic overflow conditions that can be exploited by the contract owner or any entity with owner privileges. The integer overflow occurs during the token minting process where the balance calculation fails to validate that the resulting value remains within the valid range of the data type, typically a uint256 in Ethereum smart contracts. This allows an attacker with owner access to manipulate token balances by performing arithmetic operations that wrap around to unexpected values, effectively enabling the creation of arbitrary token balances for any user address.
The operational impact of this vulnerability extends beyond simple balance manipulation, creating a significant risk to the token ecosystem and user funds. Contract owners can exploit this flaw to generate unlimited token balances for themselves or other users, potentially leading to massive dilution of token value or unauthorized access to funds. The vulnerability's exploitation directly violates the fundamental principles of tokenomics and financial security that smart contracts are designed to enforce, as it undermines the integrity of the token distribution mechanism. Users who hold tokens in this system face potential loss of funds or value as malicious actors could manipulate their balances or create artificial inflation through unauthorized minting operations. The vulnerability also impacts the contract's overall trust model, as it demonstrates a critical failure in the security controls that should protect against unauthorized modifications to token distributions and user balances.
Mitigation strategies for this vulnerability should focus on implementing comprehensive input validation and arithmetic boundary checking within the smart contract code. The recommended approach involves adding explicit overflow checks before any arithmetic operations that could potentially exceed the maximum value of the data type, utilizing Solidity's built-in overflow protection mechanisms or implementing custom validation routines that verify the integrity of all balance calculations. Security enhancements should include rigorous code auditing processes that specifically target arithmetic operations and data type handling within token contracts. Additionally, implementing proper access controls and multi-signature requirements for owner functions can limit the potential impact of such vulnerabilities. The fix should align with industry best practices for smart contract security, including adherence to the principles outlined in the Ethereum Smart Contract Security Best Practices framework and the ATT&CK framework's approach to blockchain-based threats. Regular security assessments and formal verification of smart contract code should become standard practice to prevent similar vulnerabilities from being introduced in future implementations, ensuring that the token system maintains the integrity and security that users expect from blockchain-based financial instruments.