CVE-2018-13751 in JustWallet
Summary
by MITRE
The mintToken function of a smart contract implementation for JustWallet, 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-2018-13751 resides within the mintToken function of JustWallet smart contract implementation on the Ethereum blockchain. This represents a critical security flaw that directly impacts the contract's ability to maintain accurate token balances and overall system integrity. The vulnerability stems from improper input validation and arithmetic handling within the smart contract code, creating a scenario where the contract owner can manipulate user balances arbitrarily. The issue manifests as an integer overflow condition that occurs during token minting operations, allowing unauthorized balance manipulation through carefully crafted function calls.
The technical implementation of this vulnerability aligns with CWE-190, which specifically addresses integer overflow conditions in software systems. In the context of smart contracts, this flaw enables the contract owner to exploit the mintToken function by providing malicious input parameters that cause the internal balance tracking mechanisms to overflow and wrap around to arbitrary values. The vulnerability operates at the core of the token economy by allowing the owner to set any user's balance to any desired amount, effectively compromising the fundamental accounting principles that govern cryptocurrency systems. This integer overflow occurs when the contract attempts to increment a balance variable beyond its maximum representable value, causing it to reset to zero or a negative value, which can then be manipulated to achieve the desired balance.
Operationally, this vulnerability creates severe implications for the JustWallet token ecosystem and its users. The contract owner can arbitrarily inflate or deflate user balances, potentially leading to massive financial losses for token holders who may have their funds unexpectedly altered or completely depleted. The impact extends beyond individual user accounts as it undermines the entire trust model of the decentralized application, potentially affecting token valuation and market confidence. The vulnerability also enables potential for griefing attacks where malicious actors could manipulate balances to prevent users from accessing their funds or to create artificial scarcity within the token economy. Furthermore, this flaw can be exploited to create infinite token supply conditions, where the overflow results in extremely large balance values that could disrupt the normal functioning of the token system.
Mitigation strategies for this vulnerability must address both immediate remediation and long-term architectural improvements. The primary solution involves implementing proper input validation and boundary checking within the mintToken function to prevent integer overflow conditions from occurring. Smart contract developers should utilize safe arithmetic libraries or implement explicit overflow checks before performing balance modifications. Additionally, the contract should enforce strict access controls and audit trails to monitor any balance modifications. The implementation should follow established security best practices such as those outlined in the Ethereum Smart Contract Security Best Practices guidelines and the OpenZeppelin security recommendations. Regular security auditing and formal verification of smart contract code should become standard practice to identify similar vulnerabilities before they can be exploited in production environments. The vulnerability also highlights the importance of adhering to the principle of least privilege, ensuring that contract ownership is properly managed and that administrative functions are restricted to prevent unauthorized balance manipulation.