CVE-2018-13522 in EXGROUP
Summary
by MITRE
The mintToken function of a smart contract implementation for EXGROUP, 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 • 02/27/2020
The vulnerability identified in CVE-2018-13522 represents a critical integer overflow flaw within the mintToken function of an Ethereum-based smart contract implementation for the EXGROUP token. This vulnerability resides in the core token functionality that governs the creation and distribution of new tokens within the blockchain ecosystem. The integer overflow occurs when the contract attempts to increment token balances without proper bounds checking, creating a scenario where arithmetic operations can exceed the maximum value that can be represented by the underlying data type. Such flaws are particularly dangerous in decentralized applications where financial assets are at stake and where the immutable nature of blockchain transactions makes remediation extremely challenging.
The technical implementation of this vulnerability stems from inadequate input validation and arithmetic overflow protection within the smart contract code. When the owner invokes the mintToken function, the contract performs calculations to increase user balances without implementing proper overflow detection mechanisms. This allows an attacker with owner privileges to manipulate the balance calculation in such a way that the arithmetic operation wraps around to an unintended value, potentially setting any user account to an arbitrary balance. The vulnerability specifically aligns with CWE-190, which describes integer overflow and underflow conditions, and represents a classic example of insufficient arithmetic overflow protection in smart contract implementations.
The operational impact of this vulnerability extends beyond simple balance manipulation to potentially compromise the entire token economy and user funds. An attacker with owner access can arbitrarily inflate or deflate balances of any user account, effectively enabling unauthorized token creation or destruction. This capability undermines the fundamental principles of token economics and can lead to significant financial losses for users who hold EXGROUP tokens. The vulnerability also creates potential for manipulation of token distribution, voting rights, and other contract functionalities that depend on accurate balance tracking. From an attack perspective, this represents a high-value target as it allows for direct financial gain through account manipulation without requiring complex multi-step attacks or external system compromises.
Mitigation strategies for CVE-2018-13522 must address both immediate remediation and long-term security practices within smart contract development. The primary fix involves implementing comprehensive bounds checking and overflow protection mechanisms throughout the contract code, particularly in functions that handle token balances and arithmetic operations. This includes utilizing safe math libraries such as OpenZeppelin's SafeMath implementation that automatically detect and prevent overflow conditions. Additionally, contract owners should implement proper access control mechanisms and regularly audit their smart contracts for similar vulnerabilities. The remediation process should also include thorough testing of boundary conditions and edge cases to ensure that arithmetic operations behave correctly under all circumstances. Organizations should consider implementing automated security scanning tools and formal verification methods to identify similar vulnerabilities before deployment. This vulnerability demonstrates the critical importance of adhering to secure coding practices in blockchain development and highlights the need for comprehensive security reviews before any smart contract is deployed to mainnet environments.