CVE-2018-13216 in GreenMed
Summary
by MITRE
The sell function of a smart contract implementation for GreenMed (GRMD), 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 in CVE-2018-13216 represents a critical integer overflow flaw within the sell function of the GreenMed (GRMD) smart contract implementation running on the Ethereum blockchain. This issue stems from improper input validation and arithmetic operations that fail to account for potential overflow conditions in the token selling mechanism. The vulnerability specifically manifests when the product of amount and sellPrice calculations results in zero, which fundamentally undermines the contract's ability to accurately process token sales and maintain proper asset accounting for sellers.
The technical implementation of this flaw occurs within the smart contract's sell function where mathematical operations involving token amounts and pricing parameters do not incorporate adequate overflow checking mechanisms. When the multiplication operation between the selling amount and the current sellPrice produces a result that exceeds the maximum value representable by the underlying data type, the arithmetic overflow occurs and produces an incorrect zero result. This zero value effectively nullifies the intended transaction value, causing sellers to lose their assets as the contract fails to properly reduce their token balances or credit them with the appropriate ether value. The vulnerability aligns with CWE-191, which specifically addresses integer underflow and overflow conditions in software implementations.
The operational impact of this vulnerability extends beyond simple financial loss for individual users to potentially compromising the entire token ecosystem's integrity and trustworthiness. When sellers attempt to redeem their tokens for ether, the zero result from the faulty multiplication operation means they receive no compensation for their holdings, effectively freezing their assets within the contract. This creates a cascading effect where the contract's state becomes inconsistent, potentially leading to further complications in the token's overall supply management and user trust in the platform. The vulnerability also creates opportunities for malicious actors to exploit the inconsistent state management, potentially leading to additional financial losses or system instability.
Mitigation strategies for this vulnerability require immediate implementation of comprehensive input validation and arithmetic overflow protection mechanisms within the smart contract code. The recommended approach involves incorporating explicit overflow checks before performing multiplication operations, utilizing safe math libraries such as OpenZeppelin's SafeMath implementation, and ensuring that all arithmetic operations include proper boundary validation. Additionally, the contract should implement robust error handling that prevents invalid transactions from executing and maintains consistent state management throughout all operations. Organizations should also consider implementing regular smart contract audits and continuous monitoring systems to detect similar vulnerabilities before they can be exploited, as outlined in the ATT&CK framework's approach to smart contract security. The remediation process must include thorough testing of all mathematical operations and validation of edge cases to ensure that no similar overflow conditions can occur in other functions within the contract ecosystem.