CVE-2018-13205 in ohni_2
Summary
by MITRE
The sell function of a smart contract implementation for ohni_2 (OHNI), 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 as CVE-2018-13205 resides within the sell function of ohni_2 (OHNI) smart contract implementation on the Ethereum blockchain. This represents a critical integer overflow flaw that fundamentally compromises the contract's financial integrity and user asset management capabilities. The vulnerability manifests when the multiplication operation "amount * sellPrice" produces a result that equals zero, creating a scenario where seller assets are artificially reduced without proper transactional validation or accounting.
The technical implementation of this flaw stems from improper input validation and arithmetic operation handling within the smart contract's sell function. When a user attempts to sell OHNI tokens, the contract calculates the proceeds by multiplying the token amount with the current sell price. However, due to the absence of proper overflow checks and validation mechanisms, certain combinations of amount and sellPrice values can result in arithmetic underflow or zero outputs. This condition occurs when either the amount parameter or sellPrice parameter equals zero, or when the multiplication exceeds the maximum representable value for the data type used, causing the result to wrap around to zero.
From an operational perspective, this vulnerability creates significant financial risks for token holders and contract users. Sellers who attempt to liquidate their OHNI holdings may find their asset balances incorrectly reduced, potentially resulting in complete loss of their token investments. The vulnerability affects the fundamental trust model of the smart contract by enabling unauthorized asset manipulation through carefully crafted transaction parameters. Attackers can exploit this flaw to manipulate their own asset positions or potentially drain funds from other users' accounts if the contract's access controls are insufficient.
The vulnerability aligns with CWE-190, Integer Overflow or Wraparound, which specifically addresses situations where integer arithmetic operations produce results that exceed the maximum representable value for the data type. This categorization places the issue within the broader context of arithmetic error handling in smart contracts, where similar vulnerabilities have been documented across multiple blockchain platforms. The flaw also intersects with ATT&CK technique T1548.001, which covers Abuse of Functionality, as it exploits legitimate contract functionality to achieve unintended financial outcomes through mathematical manipulation.
Mitigation strategies for this vulnerability require comprehensive code review and implementation of proper arithmetic validation mechanisms. Smart contract developers should implement explicit overflow and underflow checks before performing multiplication operations, particularly in financial functions. The use of established libraries such as OpenZeppelin's SafeMath or similar arithmetic validation tools can prevent such issues by automatically detecting and preventing overflow conditions. Additionally, thorough parameter validation should be implemented to ensure that sellPrice and amount values meet expected ranges and constraints. Regular security auditing and formal verification processes should be conducted to identify and remediate similar vulnerabilities before deployment to mainnet environments. The implementation of comprehensive testing frameworks including unit tests and integration tests specifically designed to cover edge cases in arithmetic operations will help ensure contract resilience against similar mathematical manipulation attacks.