CVE-2018-13168 in Yu Gi Oh
Summary
by MITRE
The mintToken function of a smart contract implementation for Yu Gi Oh (YGO) (Contract Name: NetkillerBatchToken), an Ethereum token, has an integer overflow that allows the owner of the contract to set the balance of an arbitrary user to any value.
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Analysis
by VulDB Data Team • 02/25/2020
The vulnerability identified in CVE-2018-13168 represents a critical integer overflow flaw within the mintToken function of the NetkillerBatchToken smart contract implementation for the Yu Gi Oh (YGO) Ethereum token. This vulnerability stems from inadequate input validation and arithmetic operation handling within the smart contract code, specifically affecting the token's ability to manage user balances. The flaw allows the contract owner to manipulate token balances through a mathematical overflow condition that occurs when performing arithmetic operations on unsigned integers, creating a scenario where values exceed the maximum representable range and wrap around to smaller values. The vulnerability manifests when the mintToken function processes token minting operations without proper bounds checking, enabling malicious actors with owner privileges to exploit the integer overflow to set arbitrary user balances to predetermined values.
The technical exploitation of this vulnerability occurs through the manipulation of integer arithmetic within the smart contract's mintToken function, where the overflow condition can be triggered by carefully crafted inputs that cause the underlying unsigned integer variables to exceed their maximum value and wrap around to zero or negative values. This type of vulnerability falls under the CWE-190 category of Integer Overflow or Wraparound, which is classified as a fundamental weakness in the software's arithmetic operations handling. The attack vector specifically targets the contract owner's privileged position, as the vulnerability requires owner-level access to execute the malicious mintToken function calls that trigger the overflow condition. The integer overflow creates a scenario where the balance calculation becomes unpredictable and controllable, allowing an attacker to manipulate the token distribution and potentially drain or manipulate the token supply in ways that violate the intended contract behavior and user expectations.
The operational impact of this vulnerability extends beyond simple balance manipulation to potentially compromise the entire token ecosystem and user trust in the smart contract implementation. When exploited, the vulnerability enables the contract owner to artificially inflate or deflate user balances, creating an environment where token ownership can be manipulated without proper authorization or transparency. This manipulation directly affects the token's economic model and can lead to significant financial losses for users who hold the affected tokens. The vulnerability also introduces risks related to token transfer operations, as users with manipulated balances may experience unexpected behavior when attempting to transfer or trade their tokens. Additionally, the exploit can undermine the fundamental principles of blockchain technology by enabling unauthorized balance modifications that contradict the immutable nature of blockchain transactions and smart contract operations.
Mitigation strategies for this vulnerability require immediate code-level fixes that address the integer overflow condition through proper input validation and arithmetic boundary checks. The most effective approach involves implementing explicit overflow detection mechanisms using require statements or conditional checks that validate the arithmetic operations before execution, ensuring that values remain within acceptable ranges. Smart contract developers should adopt defensive programming practices including the use of safe math libraries that automatically handle overflow conditions or implement explicit checks before performing arithmetic operations. The vulnerability also necessitates a comprehensive review of all arithmetic operations within the smart contract, particularly those involving user balances, token transfers, and minting functions. Organizations should implement proper access control measures to limit the privileges of contract owners and establish multi-signature requirements for critical operations. Additionally, regular security audits and formal verification processes should be conducted to identify similar vulnerabilities in smart contract implementations, as outlined in the ATT&CK framework's approach to smart contract security weaknesses and the importance of proper code review practices for blockchain-based applications.