CVE-2018-13737 in AnovaBace
Summary
by MITRE
The mintToken function of a smart contract implementation for AnovaBace, 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-2018-13737 represents a critical integer overflow flaw within the mintToken function of the AnovaBace Ethereum token smart contract implementation. This vulnerability resides in the fundamental mathematical operations of the smart contract code where insufficient input validation and overflow protection mechanisms allow malicious actors to manipulate token balances. The flaw specifically affects the token's minting functionality, which is designed to create new tokens and distribute them to users. When the mintToken function processes user inputs without proper boundary checks, it creates conditions where arithmetic operations can exceed the maximum value that can be represented by the underlying data types, leading to unexpected behavior and potential exploitation.
The technical execution of this vulnerability stems from the absence of proper overflow detection mechanisms within the smart contract's arithmetic operations. In Ethereum smart contracts, integer overflows occur when mathematical operations exceed the maximum value that can be stored in a variable, causing the value to wrap around to zero or negative numbers. The mintToken function in AnovaBace fails to implement adequate safeguards such as overflow checks or use of safe math libraries, allowing an attacker to manipulate the token supply and user balances. This vulnerability directly maps to CWE-191, which specifically addresses integer underflow and overflow conditions, and can be classified under the broader category of CWE-682, which encompasses incorrect arithmetic operations. The attack vector leverages the contract owner's privileged position to execute the mintToken function with maliciously crafted parameters that exploit the integer overflow to manipulate token balances beyond normal operational limits.
The operational impact of this vulnerability extends far beyond simple balance manipulation, creating significant risks for token holders and the overall ecosystem. An attacker with access to the contract owner account can arbitrarily set any user's token balance to any desired value, potentially allowing them to create unlimited tokens or drain existing balances. This capability fundamentally undermines the integrity of the token economy and can lead to complete loss of value for legitimate users. The vulnerability enables several attack scenarios including the creation of infinite tokens, manipulation of token distributions, and potential theft of user funds through balance manipulation. From an operational security perspective, this flaw represents a severe weakness in the smart contract's access control and input validation mechanisms, as it allows a privileged user to bypass normal token creation and distribution rules. The implications for the Ethereum token ecosystem are substantial, as such vulnerabilities can erode trust in smart contract implementations and potentially lead to financial losses for users and organizations relying on these systems.
Mitigation strategies for this vulnerability require immediate implementation of proper integer overflow protection mechanisms within the smart contract code. The most effective approach involves incorporating safe math libraries or implementing explicit overflow checks before any arithmetic operations within the mintToken function. Organizations should ensure that all mathematical operations include proper boundary validation and that the contract enforces strict input validation for all user-supplied parameters. Additionally, the contract should implement comprehensive access control measures to limit who can execute the mintToken function and consider using multi-signature wallets for privileged operations. From a security operations standpoint, regular smart contract audits and formal verification processes should be implemented to identify similar vulnerabilities before deployment. The remediation process should also include thorough testing of edge cases and boundary conditions to ensure that all potential overflow scenarios are properly handled. Organizations should reference established security frameworks such as the OpenZeppelin safe math libraries and follow best practices outlined in the Ethereum Smart Contract Security Best Practices guidelines to prevent similar vulnerabilities from occurring in future implementations. The vulnerability also highlights the importance of implementing proper code review processes and automated security scanning tools to identify integer overflow conditions and other common smart contract security flaws.