CVE-2018-13085 in FreeCoin
Summary
by MITRE
The mintToken function of a smart contract implementation for FreeCoin (FREE), 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 • 02/24/2020
The vulnerability identified as CVE-2018-13085 represents a critical integer overflow flaw within the mintToken function of the FreeCoin (FREE) smart contract deployed on the Ethereum blockchain. This vulnerability stems from improper input validation and arithmetic handling within the contract's token minting mechanism, creating a fundamental security weakness that directly impacts the contract's integrity and user fund safety. The flaw allows the contract owner to manipulate user balances arbitrarily, effectively enabling unauthorized fund manipulation and potentially leading to complete loss of user assets. The vulnerability manifests when the mintToken function processes token minting operations without proper overflow checks, permitting the owner to specify any balance value for target users through crafted function parameters.
This technical weakness falls under the CWE-190 category of integer overflow and under CWE-699 for software development security issues, specifically affecting the Ethereum smart contract ecosystem. The vulnerability operates at the core of the contract's arithmetic operations where the mintToken function fails to validate that the resulting token balance will not exceed the maximum value representable by the underlying data type. This allows the contract owner to exploit the mathematical properties of integer arithmetic to manipulate balances beyond normal operational limits. The ATT&CK framework categorizes this as a privilege escalation technique where an attacker with owner privileges can manipulate contract state to achieve unauthorized outcomes, specifically under the T1078 Privilege Escalation tactic.
The operational impact of CVE-2018-13085 is severe and multifaceted, affecting both individual user accounts and the overall token economy. When exploited, the vulnerability allows the contract owner to set any user's balance to an arbitrary value, including potentially infinite balances or negative values that could destabilize the entire token system. This creates immediate financial risk for users who may lose their funds or face unexpected balance manipulations, while also undermining trust in the token's legitimacy and the underlying blockchain infrastructure. The vulnerability's exploitation does not require external network access or complex attack chains, making it particularly dangerous as it can be triggered directly by the contract owner with minimal technical expertise. The financial implications extend beyond individual users to potentially affect market stability and regulatory compliance for the token issuer.
Mitigation strategies for this vulnerability must address both immediate remediation and long-term security architecture improvements. The primary solution involves implementing proper integer overflow checks within the mintToken function using safe arithmetic operations or require additional validation before any balance modifications occur. Smart contract developers should utilize established libraries and frameworks that provide built-in overflow protection mechanisms, such as OpenZeppelin's SafeMath library, which prevents arithmetic operations from causing overflow conditions. Additionally, contract owners should implement comprehensive access controls and audit procedures to prevent unauthorized exploitation, while regular security audits should be conducted to identify similar vulnerabilities in other contract functions. The remediation process should also include thorough testing of all arithmetic operations and balance modifications, ensuring that the contract maintains consistent state throughout all operations. Furthermore, implementing proper event logging for balance changes and token minting operations enables better monitoring and detection of potential exploitation attempts.