CVE-2018-13220 in MAVCash
Summary
by MITRE
The sell function of a smart contract implementation for MAVCash, 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-2018-13220 represents a critical integer overflow flaw within the sell function of MAVCash smart contract implementation on the Ethereum blockchain. This issue stems from improper input validation and arithmetic operation handling within the contract's codebase, creating a scenario where mathematical calculations can exceed the maximum representable values for the data types used. The specific flaw occurs when the product of amount and sellPrice variables results in an overflow condition that produces a zero value, fundamentally undermining the contract's financial integrity and user asset management capabilities. Such vulnerabilities are particularly dangerous in decentralized finance applications where user funds are directly at risk.
The technical execution of this vulnerability involves the manipulation of the sell function's internal calculations, where the multiplication operation between amount and sellPrice variables fails to account for potential overflow conditions. When these variables exceed the maximum value that can be stored in their designated data types, the arithmetic operation wraps around to zero, effectively nullifying the intended transaction value. This behavior violates the fundamental principles of secure smart contract development and demonstrates a lack of proper boundary checking mechanisms. The vulnerability aligns with CWE-190, which specifically addresses integer overflow and underflow conditions in software systems, making it a classic example of improper integer handling in blockchain smart contracts.
The operational impact of this vulnerability extends beyond simple financial loss to encompass complete trust erosion in the affected smart contract system. Users who attempt to sell their MAVCash tokens may find their assets reduced to zero or significantly diminished due to the overflow condition, creating a scenario where legitimate transactions fail to execute as intended. The zero result from the multiplication operation effectively renders the sell function useless for transactions involving certain token amounts, while potentially allowing malicious actors to exploit the condition for unintended financial gain. This vulnerability directly impacts the contract's ability to maintain accurate accounting and asset tracking, creating a persistent threat to user funds and system integrity.
Mitigation strategies for this vulnerability require comprehensive code review and implementation of proper integer overflow protection mechanisms within the smart contract. Developers must implement explicit checks before arithmetic operations to ensure that multiplication results remain within acceptable bounds, utilizing techniques such as require statements or SafeMath libraries that are standard in Ethereum smart contract development. The fix should include validation of input parameters and proper handling of edge cases where arithmetic operations might produce unexpected results. Additionally, thorough testing procedures including fuzz testing and formal verification methods should be employed to identify similar vulnerabilities before deployment. This remediation approach aligns with ATT&CK technique T1587.001, which addresses the exploitation of software vulnerabilities in blockchain systems, emphasizing the importance of proper input validation and secure coding practices in preventing such attacks.