CVE-2018-11446 in Gold Reward
Summary
by MITRE
The buy function of a smart contract implementation for Gold Reward (GRX), an Ethereum ERC20 token, allows a potential trap that could be used to cause financial damage to the buyer because of overflow of the multiplication of its argument amount and a manipulable variable buyPrice, aka the "tradeTrap" issue.
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Analysis
by VulDB Data Team • 02/21/2020
The vulnerability identified as CVE-2018-11446 represents a critical arithmetic overflow issue within the buy function of the Gold Reward (GRX) smart contract implementation on the Ethereum blockchain. This flaw stems from improper handling of integer multiplication operations that combine a user-provided amount parameter with a manipulable buyPrice variable, creating a scenario where the mathematical operation can exceed the maximum value that can be stored in the designated data type. The vulnerability specifically affects the token's trading mechanism, where the buy function calculates the total cost for purchasing GRX tokens by multiplying the requested amount by the current buyPrice. When these two variables are multiplied together without adequate overflow checks, the result can wrap around to a much smaller value due to the finite nature of integer storage in smart contracts. This behavior creates a fundamental security risk because attackers can manipulate the buyPrice variable to control the multiplication outcome, potentially causing unexpected financial consequences for users who attempt to purchase tokens.
The technical execution of this vulnerability aligns with CWE-191, which addresses integer underflow and overflow conditions, and specifically demonstrates how improper input validation and arithmetic operations can lead to unintended behavior in smart contract systems. The attack vector exploits the fact that the buyPrice variable is manipulable, allowing malicious actors to set it to values that, when multiplied by the user-specified amount, result in overflow conditions. This creates a situation where the contract's internal accounting becomes corrupted, potentially allowing attackers to purchase tokens at prices that are orders of magnitude lower than intended, or conversely, cause the transaction to fail in unexpected ways. The vulnerability's impact extends beyond simple financial loss as it fundamentally undermines the trust in the token's trading mechanism and can lead to complete loss of funds for unsuspecting users who engage in transactions during the vulnerable period.
The operational impact of this vulnerability manifests in several ways that directly affect both individual users and the broader Ethereum ecosystem. Users who attempt to purchase GRX tokens through the affected buy function may experience financial losses due to the overflow behavior, where their transaction costs are calculated incorrectly, resulting in either excessive token acquisition at reduced cost or complete transaction failures. The vulnerability also creates a potential for systematic exploitation, as attackers can monitor the blockchain for users attempting to purchase tokens and then manipulate the buyPrice variable to maximize their profit margins. This type of attack can lead to significant market manipulation and loss of confidence in the token's legitimacy. Additionally, the vulnerability demonstrates a common pattern in smart contract development where developers fail to implement proper overflow protection mechanisms, highlighting the need for comprehensive security testing and adherence to established best practices in blockchain development. The attack surface is particularly concerning because it operates at the core trading function of the token, making it accessible to any user who attempts to purchase GRX tokens.
Mitigation strategies for this vulnerability must address both immediate and long-term security concerns within the smart contract implementation. The most direct solution involves implementing proper overflow checks using safe math libraries or explicit validation before performing arithmetic operations, ensuring that the multiplication of amount and buyPrice variables cannot exceed the maximum value for the target data type. Developers should also consider implementing access controls to prevent unauthorized manipulation of the buyPrice variable, and establish proper input validation for all user-provided parameters. The remediation process should include thorough code review and testing to ensure that all arithmetic operations are protected against overflow conditions, following the principles outlined in the solidity documentation and industry best practices for smart contract security. Organizations should also implement monitoring systems to detect unusual patterns in token trading that might indicate exploitation attempts, and establish incident response procedures for addressing similar vulnerabilities in other smart contracts. This vulnerability serves as a reminder of the critical importance of comprehensive security testing, including formal verification and penetration testing, before deploying smart contracts to production environments, as outlined in various cybersecurity frameworks and standards that emphasize the need for robust security controls in blockchain-based applications.