CVE-2018-13204 in ETHERCASH
Summary
by MITRE
The sell function of a smart contract implementation for ETHERCASH (ETC), an Ethereum token, has an integer overflow in which "amount * sellPrice" can be zero, consequently reducing a seller's assets.
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Analysis
by VulDB Data Team • 02/25/2020
The vulnerability identified as CVE-2018-13204 affects the ETHERCASH (ETC) smart contract implementation on the Ethereum blockchain, representing a critical integer overflow flaw that directly impacts asset management and financial transactions within the token ecosystem. This vulnerability resides within the sell function of the smart contract, where the mathematical operation amount * sellPrice can produce an incorrect result due to integer overflow conditions. The flaw occurs when the multiplication of two integer values exceeds the maximum value that can be represented within the allocated storage space, causing the result to wrap around to zero or another unexpected value. Such behavior fundamentally undermines the contract's ability to accurately calculate transaction values and maintain proper accounting of seller assets.
The technical implementation of this vulnerability stems from the absence of proper overflow checks within the sell function's arithmetic operations. When the sell function processes token redemption requests, it multiplies the number of tokens being sold (amount) by the current sell price (sellPrice) to determine the total value to be transferred to the seller. In scenarios where the product of these two values exceeds the maximum representable integer value, the overflow condition causes the result to be truncated or wrapped, potentially resulting in a zero value. This mathematical anomaly directly enables attackers to manipulate the sell function to bypass normal transaction processing, effectively allowing them to reduce or eliminate the value of assets that should be transferred to sellers during token redemption.
The operational impact of this vulnerability extends beyond simple financial miscalculations to create potential for significant asset loss and system manipulation within the ETHERCASH token ecosystem. When the multiplication operation results in zero due to overflow conditions, sellers receive no compensation for their tokens, effectively draining their assets while the contract maintains incorrect internal state. This flaw creates a scenario where legitimate token holders could lose their entire investment in the token without any compensation, as the system fails to properly execute sell transactions. The vulnerability also introduces uncertainty and instability into the token's market dynamics, potentially causing trust issues among users and creating opportunities for exploitation that could destabilize the entire token economy.
Security professionals should address this vulnerability by implementing comprehensive integer overflow protections within the smart contract's arithmetic operations. The recommended mitigation involves adding explicit overflow checks before any multiplication operations, ensuring that the result of amount * sellPrice remains within acceptable integer bounds. This approach aligns with the common weakness enumeration CWE-190, which specifically addresses integer overflow and underflow conditions in software implementations. Additionally, the remediation strategy should incorporate proper input validation and boundary checking mechanisms that prevent malicious actors from exploiting the mathematical properties of integer arithmetic. The ATT&CK framework's technique T1059.001 for command and scripting interpreter could be relevant if attackers attempt to exploit this vulnerability through automated smart contract interactions or manipulation of transaction parameters to trigger the overflow condition.
The broader implications of this vulnerability highlight the critical importance of rigorous smart contract auditing and security testing in blockchain-based financial systems. The flaw demonstrates how seemingly simple arithmetic operations can create devastating security implications when proper safeguards are absent from decentralized applications. Organizations implementing blockchain-based solutions must recognize that vulnerabilities in smart contract arithmetic operations can lead to irreversible financial losses and system compromise. The remediation process should include comprehensive code review procedures that specifically examine all mathematical operations for potential overflow conditions, along with systematic testing using various input parameters to ensure that edge cases do not result in unintended behavior. This vulnerability serves as a stark reminder of the necessity for security-conscious development practices and thorough validation of all contract logic before deployment to production environments.