CVE-2018-13197 in Welfare Token Fund
Summary
by MITRE
The sell function of a smart contract implementation for Welfare Token Fund (WTF), 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-2018-13197 resides within the sell function of the Welfare Token Fund (WTF) smart contract deployed on the Ethereum blockchain. This represents a critical integer overflow flaw that fundamentally compromises the contract's financial integrity and user asset protection mechanisms. The vulnerability manifests 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 handling of integer arithmetic. This issue directly violates the fundamental principles of secure smart contract development and demonstrates a failure to implement proper input validation and arithmetic overflow protection mechanisms.
The technical implementation flaw stems from the contract's inability to properly validate or constrain the multiplication operation between the token amount and the sell price, allowing for scenarios where the calculation produces an unexpected zero result. When this occurs, the seller's assets are effectively reduced or lost within the contract's accounting system, creating a direct financial loss for users who attempt to sell their tokens. This vulnerability operates at the intersection of multiple security domains including smart contract security, blockchain cryptography, and financial transaction integrity. The flaw aligns with CWE-190, which specifically addresses integer overflow and underflow conditions, and represents a classic example of how improper arithmetic handling can lead to catastrophic financial consequences in decentralized applications.
The operational impact of this vulnerability extends beyond individual user losses to potentially destabilize the entire token ecosystem and undermine trust in the smart contract platform. When users discover that their assets are being incorrectly calculated or reduced during token sales, it creates a ripple effect of distrust that can damage the reputation of the entire project. The vulnerability also demonstrates the critical importance of thorough security auditing in blockchain environments where financial transactions are irreversible and where code execution cannot be easily modified once deployed. Attackers could potentially exploit this vulnerability systematically to drain funds from multiple users, making it a particularly dangerous flaw in a financial application. The implications of such a vulnerability also extend to the broader Ethereum ecosystem, as it highlights the need for more robust security frameworks and testing methodologies before deploying smart contracts to mainnet environments.
Mitigation strategies for this vulnerability require immediate remediation through contract reimplementation that includes proper integer overflow protection mechanisms such as the use of safe math libraries, input validation checks, and explicit boundary condition testing. Organizations should implement comprehensive smart contract security auditing processes that include formal verification techniques and extensive testing of arithmetic operations. The fix should incorporate proper overflow detection using constructs like require statements to validate that multiplication operations produce meaningful results, and ensure that all user balances are properly tracked and maintained. Additionally, the vulnerability underscores the necessity of following established security standards and best practices such as those outlined in the Ethereum Smart Contract Security Best Practices guidelines, which emphasize the importance of defensive programming and comprehensive testing before deployment. The incident serves as a critical reminder that blockchain-based financial systems must incorporate multiple layers of security controls to prevent even seemingly minor arithmetic flaws from causing significant financial harm.