CVE-2018-13593 in CardToken
Summary
by MITRE
The mintToken function of a smart contract implementation for CardToken, 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-2018-13593 represents a critical integer overflow flaw within the mintToken function of the CardToken smart contract implementation on the Ethereum blockchain. This vulnerability stems from inadequate input validation and arithmetic overflow handling within the contract's codebase, creating a scenario where the contract owner can manipulate token balances of any user account to arbitrary values. The flaw exists in the core token minting mechanism that should logically restrict new token creation to legitimate user accounts while maintaining proper balance accounting.
The technical implementation of this vulnerability manifests through improper handling of unsigned integer arithmetic operations within the mintToken function. When the contract attempts to increment token balances or perform arithmetic operations on token quantities, the lack of overflow checks allows values to wrap around to zero or negative numbers, creating predictable patterns that the contract owner can exploit. This type of vulnerability maps directly to CWE-190, which specifically addresses integer overflow and underflow conditions in software implementations. The vulnerability enables a privileged user to bypass normal token distribution mechanisms and directly manipulate account balances through controlled arithmetic operations that should have been protected against such manipulation.
The operational impact of this vulnerability extends beyond simple financial manipulation to encompass potential systemic risks within the token ecosystem. An attacker with owner privileges can increase any user's balance to extremely high values, potentially causing the total supply to exceed maximum integer limits or creating situations where the contract becomes unusable due to arithmetic errors. This vulnerability also undermines the fundamental trust model of the token system, as users cannot rely on the integrity of their token balances. The exploitation of this vulnerability can lead to immediate financial loss for affected users and may require complete contract replacement or emergency hard forks to address the issue. Additionally, the vulnerability demonstrates poor security practices in smart contract development, including inadequate testing for edge cases and insufficient validation of user inputs.
Mitigation strategies for this vulnerability must address both immediate remediation and long-term development practices. The most direct fix involves implementing proper integer overflow protection using modern solidity features such as require statements with bounds checking or employing safe math libraries that automatically handle overflow conditions. The contract owner should also implement comprehensive access control measures and consider using multi-signature wallets for critical operations to prevent unauthorized exploitation. Organizations should adopt security best practices aligned with the ATT&CK framework's defense against smart contract vulnerabilities by implementing proper input validation, conducting thorough code reviews, and utilizing automated security testing tools. Regular security audits and penetration testing should be mandatory for all smart contract deployments, particularly those handling financial assets. The vulnerability also highlights the importance of following established security standards such as those outlined in the OpenZeppelin security guidelines and implementing proper testing procedures including unit tests that specifically target edge cases and overflow scenarios.