CVE-2018-13203 in SwapToken
Summary
by MITRE
The sellBuyerTokens function of a smart contract implementation for SwapToken, 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-2018-13203 represents a critical integer overflow flaw within the sellBuyerTokens function of a SwapToken Ethereum smart contract implementation. This vulnerability falls under the CWE-190 category of integer overflow and under the ATT&CK technique T1210 for exploitation of remote services. The flaw occurs when the mathematical operation "amount * sellPrice" produces a result that cannot be properly represented within the allocated integer data type, leading to unexpected behavior in the contract's asset management logic.
The technical implementation of this vulnerability stems from improper input validation and arithmetic handling within the smart contract's sellBuyerTokens function. When a seller attempts to exchange tokens, the contract performs a multiplication operation between the token amount and the sell price to determine the value of the transaction. If this multiplication results in an integer overflow condition, the calculation may produce a zero value instead of the expected positive result. This zero value effectively nullifies the seller's intended asset transfer, allowing attackers to manipulate the contract's accounting system and potentially drain funds from seller accounts.
The operational impact of this vulnerability extends beyond simple financial loss, as it fundamentally compromises the integrity of the token exchange mechanism within the SwapToken platform. Attackers can exploit this condition to execute unauthorized transactions where the seller's assets are incorrectly calculated or reduced to zero, effectively enabling theft of tokens from legitimate users. The vulnerability creates a scenario where malicious actors can manipulate the sellPrice parameter or the amount parameter to force the overflow condition, resulting in unauthorized asset depletion.
Mitigation strategies for this vulnerability require comprehensive contract redesign and implementation of proper integer overflow protection mechanisms. Developers must implement explicit bounds checking and arithmetic validation before performing multiplication operations, particularly when dealing with user-supplied values. The use of established safe math libraries such as OpenZeppelin's SafeMath or similar implementations can prevent such overflow conditions by automatically detecting and reverting invalid arithmetic operations. Additionally, thorough code auditing and formal verification processes should be implemented to identify similar vulnerabilities in other smart contract functions. The vulnerability also highlights the importance of adhering to secure coding practices as outlined in the OWASP Secure Coding Practices and the Ethereum Smart Contract Security Best Practices guidelines, which emphasize the necessity of robust input validation and mathematical operation safety in blockchain applications.