CVE-2018-13491 in Carrot
Summary
by MITRE
The mintToken function of a smart contract implementation for Carrot, 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.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 02/27/2020
The vulnerability identified in CVE-2018-13491 represents a critical integer overflow flaw within the mintToken function of the Carrot Ethereum token smart contract implementation. This vulnerability resides in the core token functionality that allows for the creation and distribution of new tokens within the blockchain ecosystem. The flaw specifically manifests when the contract attempts to increment token balances through arithmetic operations that exceed the maximum value that can be represented by the underlying data types. The integer overflow occurs because the smart contract does not properly validate or constrain the arithmetic operations involved in token minting, creating a scenario where malicious actors can manipulate the token supply mechanism. This vulnerability directly violates the fundamental principles of secure smart contract development as outlined in the Ethereum Smart Contract Security Best Practices and represents a classic example of improper input validation and arithmetic operation handling.
The technical exploitation of this vulnerability enables an attacker with owner privileges to manipulate token balances in ways that were never intended by the contract design. When the mintToken function processes token creation requests, the integer overflow allows for the manipulation of balance calculations, potentially enabling the owner to set any user's balance to an arbitrary value including zero, maximum values, or negative balances. This flaw operates at the core level of the token's accounting system and can be leveraged to create infinite token supplies or manipulate user holdings without detection. The vulnerability is classified as CWE-191, Integer Underflow/Overflow, which specifically addresses the issue of arithmetic operations that produce results outside the range of the data type used to store them. The operational impact extends beyond simple balance manipulation as it can potentially compromise the entire economic model of the token, allowing for unauthorized wealth redistribution or token supply manipulation that directly affects all token holders.
The security implications of this vulnerability extend far beyond the immediate technical flaw, as it fundamentally undermines trust in the smart contract's integrity and the token's economic stability. An attacker exploiting this vulnerability could potentially drain token reserves, manipulate market prices through artificial supply manipulation, or create scenarios where certain users gain disproportionate token holdings. The impact on token holders includes potential loss of funds, market manipulation, and complete erosion of confidence in the token's governance and security. This vulnerability aligns with ATT&CK technique T1059.006 for Smart Contract Manipulation, where adversaries exploit weaknesses in blockchain contract implementations to gain unauthorized control over assets. The vulnerability also relates to T1548.005 for Account Manipulation and T1566.001 for Phishing, as compromised contracts can be used to facilitate further attacks on users and other systems. The exploitability of this vulnerability is particularly concerning because it requires only owner privileges to execute, meaning that if the contract owner's private key is compromised or if there are governance issues within the project, the entire token ecosystem becomes vulnerable to manipulation.
Mitigation strategies for this vulnerability must focus on implementing proper input validation and arithmetic operation constraints within the smart contract code. Developers should utilize safe arithmetic libraries such as OpenZeppelin's SafeMath or similar implementations that prevent overflow and underflow conditions through built-in checks before performing arithmetic operations. The contract should validate all inputs to the mintToken function, particularly the amount parameter, and ensure that balance calculations cannot exceed the maximum representable values for the data types used. Additionally, implementing comprehensive testing including fuzz testing and formal verification can help identify similar vulnerabilities before deployment. The contract should also include proper access controls and audit trails to monitor any balance modifications, and regular security audits should be conducted to ensure that no new vulnerabilities are introduced during contract upgrades or modifications. The vulnerability highlights the importance of following security standards such as those outlined in the OpenZeppelin Security Best Practices and the Solidity documentation's recommendations for preventing integer overflow conditions in smart contract development.