CVE-2018-13221 in Extreme Coin
Summary
by MITRE
The sell function of a smart contract implementation for Extreme Coin (XT) (Contract Name: ExtremeToken), 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-2018-13221 affects the Extreme Coin (XT) smart contract implementation on the Ethereum blockchain, specifically within the sell function of the ExtremeToken contract. This represents a critical integer overflow issue that fundamentally compromises the contract's financial integrity and asset management capabilities. The flaw occurs when the contract attempts to calculate the value of tokens being sold through the mathematical operation "amount * sellPrice" where the result can unexpectedly evaluate to zero due to improper integer handling.
The technical implementation of this vulnerability stems from inadequate input validation and arithmetic overflow protection within the smart contract's sell function. When a user attempts to sell tokens, the contract calculates the proceeds by multiplying the token amount with the current sell price. However, the contract fails to properly validate that the multiplication result will not exceed the maximum value representable by the integer data type, or more specifically, when the multiplication results in an arithmetic underflow or zero value due to integer overflow conditions. This vulnerability directly maps to CWE-191, which identifies integer underflow (wrap under) as a common weakness in software implementations, particularly in blockchain smart contracts where mathematical operations must maintain strict financial accuracy.
The operational impact of this vulnerability is severe and directly affects all users attempting to sell XT tokens through the affected contract. When the multiplication operation results in zero due to overflow conditions, sellers effectively lose their tokens without receiving any compensation, as the contract fails to properly calculate or transfer the appropriate value. This creates a systematic financial loss mechanism where sellers can be completely drained of their token holdings while the contract's state remains inconsistent. The vulnerability also potentially enables malicious actors to manipulate the contract's financial state, as the zero-value calculation can be exploited to artificially inflate or deflate the contract's token reserves, undermining the fundamental trust model of the cryptocurrency system.
Security professionals should consider this vulnerability in the context of broader blockchain security frameworks and attack patterns. The flaw aligns with ATT&CK technique T1499.001, which covers unauthorized access to digital assets through smart contract vulnerabilities, and represents a classic example of how improper arithmetic handling can lead to financial loss in decentralized applications. The vulnerability also demonstrates the importance of proper integer overflow detection and the need for comprehensive testing of mathematical operations in smart contracts. Organizations should implement rigorous contract auditing processes that include formal verification techniques and automated testing for arithmetic operations to prevent similar issues in future deployments. The incident highlights the critical need for adherence to security best practices in blockchain development, particularly regarding the handling of financial calculations and the implementation of proper overflow protection mechanisms.