CVE-2018-13749 in FinalToken
Summary
by MITRE
The mintToken function of a smart contract implementation for FinalToken, 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 • 03/03/2020
The vulnerability identified as CVE-2018-13749 resides within the mintToken function of a smart contract implementation for FinalToken, an Ethereum-based token contract. This flaw represents a critical integer overflow vulnerability that fundamentally compromises the contract's integrity and security model. The vulnerability allows the contract owner to manipulate user balances arbitrarily, effectively undermining the core principles of decentralized finance and token economics. The issue manifests specifically within the mintToken function where improper input validation and arithmetic operations create conditions for overflow scenarios that can be exploited by the contract owner to manipulate token distributions.
The technical flaw stems from the absence of proper overflow checks in the mintToken function implementation. When the contract owner invokes this function to mint new tokens for a specific user, the underlying arithmetic operations fail to validate whether the resulting balance would exceed the maximum value that can be represented by the data type used for storing token balances. This vulnerability directly maps to CWE-190, which describes integer overflow and underflow conditions, and specifically aligns with CWE-682, representing incorrect use of mathematical operations. The Ethereum blockchain environment, with its deterministic execution model and immutable transaction processing, makes such vulnerabilities particularly dangerous as they can be exploited to create unlimited token supply or manipulate user balances without detection.
The operational impact of this vulnerability extends far beyond simple balance manipulation, creating a comprehensive security breach that affects the entire token ecosystem. Contract owners can arbitrarily set user balances to any value, including zero, negative values, or extremely large amounts, effectively allowing them to drain funds from other users or create artificial wealth distributions. This capability enables sophisticated attack vectors such as creating infinite token supply, manipulating market prices through artificial balance manipulation, or even executing denial-of-service attacks by setting balances to prevent user transactions. The vulnerability also introduces risks related to governance and trust, as users lose confidence in the contract's ability to maintain fair and accurate token distributions.
The exploitability of this vulnerability requires the attacker to possess the contract owner privileges, making it a privilege escalation issue rather than a general access vulnerability. However, the implications are severe as it allows the owner to manipulate the token economy in ways that can cause significant financial damage to users and the broader ecosystem. The vulnerability can be exploited through simple transaction calls to the mintToken function, making it particularly dangerous as it requires minimal technical expertise to execute. Organizations and users should implement immediate mitigations including contract audits, proper overflow checking mechanisms, and potentially contract upgrades to prevent such manipulations. The vulnerability also highlights the importance of adhering to established security standards such as those defined in the OpenZeppelin security guidelines and emphasizes the need for comprehensive testing including formal verification approaches to prevent similar issues in future smart contract implementations.
This vulnerability demonstrates the critical importance of robust input validation and arithmetic operation safety in smart contract development. The lack of proper integer overflow protection in the mintToken function creates a fundamental weakness that can be exploited to manipulate the token economy. Security practitioners should ensure that all arithmetic operations in smart contracts include appropriate overflow and underflow checks, particularly when dealing with user balances and token minting operations. The vulnerability also underscores the need for comprehensive security testing including both automated tools and manual code review processes to identify such critical flaws before deployment. Organizations should also consider implementing access control mechanisms and multi-signature requirements for critical contract functions to reduce the risk of unauthorized privilege escalation attacks.