CVE-2018-13087 in Coinstar
Summary
by MITRE
The mintToken function of a smart contract implementation for Coinstar (CSTR), 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 • 02/24/2020
The vulnerability identified in CVE-2018-13087 represents a critical integer overflow flaw within the mintToken function of the Coinstar (CSTR) Ethereum token smart contract implementation. This 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 flaw exists in the core token management functionality, specifically affecting how the contract handles token minting operations and subsequent balance updates. The vulnerability is particularly dangerous because it grants the contract owner elevated privileges beyond normal operational boundaries, allowing for unauthorized balance manipulation that could compromise the entire token economy.
The technical implementation of this vulnerability manifests through an integer overflow condition that occurs during the mintToken function execution. When processing token minting requests, the smart contract fails to properly validate or constrain the input parameters that determine the target user's balance increment. This allows the contract owner to submit malicious parameters that cause arithmetic overflow conditions, effectively bypassing normal balance calculation mechanisms. The vulnerability is classified under CWE-190 as an integer overflow or wraparound, specifically occurring in the context of Ethereum smart contract arithmetic operations. The overflow enables the attacker to manipulate the balance storage variables to arbitrary values, potentially leading to unlimited token creation or unauthorized balance transfers.
Operationally, this vulnerability creates significant risks for the Coinstar token ecosystem and its users. The contract owner can exploit this flaw to inflate any user's token balance to extremely high values, potentially causing the token supply to become artificially inflated beyond intended limits. This manipulation could enable the owner to drain the contract's token reserves or create artificial market distortions. The impact extends beyond simple balance manipulation as it undermines the fundamental trust in the token's integrity and the smart contract's ability to maintain accurate accounting. Users may lose confidence in the token's value, and the entire token economy could be compromised through systematic exploitation of this vulnerability. The vulnerability also enables potential denial-of-service scenarios where the contract's state becomes corrupted through extreme balance values.
Mitigation strategies for this vulnerability require immediate remediation of the smart contract code through proper input validation and arithmetic boundary checking. The mintToken function must implement comprehensive parameter validation to prevent overflow conditions, including explicit checks for maximum balance limits and proper overflow handling mechanisms. Developers should employ safe arithmetic libraries or implement checked arithmetic operations that prevent overflow conditions from occurring. Additionally, the contract should implement proper access controls and audit trails to monitor any balance modifications. The fix should align with Ethereum best practices and security standards such as those outlined in the Solidity documentation for preventing integer overflows. Regular security audits and formal verification techniques should be implemented to prevent similar vulnerabilities in future smart contract deployments. The vulnerability demonstrates the critical importance of thorough testing and validation in smart contract development environments, particularly when handling financial operations and user balances.