CVE-2018-13162 in ALEX
Summary
by MITRE
The mintToken function of a smart contract implementation for ALEX, 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-2018-13162 represents a critical integer overflow flaw within the mintToken function of the ALEX Ethereum token smart contract implementation. This vulnerability stems from improper input validation and arithmetic handling within the smart contract code, creating a condition where the owner can manipulate token balances arbitrarily. The flaw allows for the creation of tokens beyond the intended limits, effectively enabling the contract owner to inflate or deflate user balances at will. Such a vulnerability fundamentally undermines the integrity and security of the token economy, as it provides the contract owner with unprecedented control over the distribution and value of tokens within the system.
The technical nature of this vulnerability aligns with CWE-190, which describes integer overflow conditions where an attacker can cause an integer to wrap around to a smaller or negative value when performing arithmetic operations. In the context of Ethereum smart contracts, this manifests as the mintToken function failing to properly validate the parameters passed to it, particularly when dealing with large integer values that exceed the maximum representable value for the data type used. The vulnerability operates through the manipulation of the token supply mechanism, allowing the owner to bypass normal token minting constraints and directly control account balances through the contract's administrative functions.
The operational impact of this vulnerability extends far beyond simple balance manipulation, creating significant risks for token holders and the broader ecosystem. An attacker with owner privileges could potentially drain liquidity from user accounts, inflate their own holdings to manipulate market prices, or create artificial scarcity by reducing other users' balances. This vulnerability effectively grants the contract owner the ability to perform unauthorized transactions on behalf of other users, creating a fundamental breach of trust within the token system. The implications for user funds and market stability are severe, as this flaw enables the owner to effectively control the token distribution without any legitimate justification, potentially leading to financial losses for token holders and undermining confidence in the entire smart contract platform.
Mitigation strategies for this vulnerability require immediate implementation of proper input validation and integer overflow protection mechanisms within the smart contract code. The mintToken function must be updated to include comprehensive parameter validation that checks for potential overflow conditions before performing arithmetic operations. This includes implementing bounds checking and using safe arithmetic libraries that can detect and prevent overflow scenarios. Additionally, the contract should enforce strict access controls and limit the owner's ability to directly manipulate user balances through administrative functions. The implementation should follow established security best practices for smart contract development, including thorough testing of edge cases and formal verification of critical functions. Organizations should also consider implementing multi-signature ownership structures and regular security audits to prevent similar vulnerabilities from being introduced in future contract implementations, aligning with the security recommendations outlined in the Ethereum Smart Contract Security Best Practices framework.