CVE-2018-13470 in BuyerToken
Summary
by MITRE
The mintToken function of a smart contract implementation for BuyerToken, 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 • 02/26/2020
The vulnerability identified as CVE-2018-13470 represents a critical integer overflow flaw within the mintToken function of the BuyerToken smart contract deployed on the Ethereum blockchain. This vulnerability stems from improper input validation and arithmetic operations that fail to account for the maximum limits of integer data types. The flaw allows an attacker with ownership privileges to manipulate token balances by setting arbitrary values for user accounts, effectively bypassing normal token distribution mechanisms. The vulnerability directly maps to CWE-190, which classifies integer overflow conditions that can lead to unexpected behavior in software applications. In the context of blockchain smart contracts, this represents a severe security risk as it enables the contract owner to manipulate token distributions and potentially compromise the integrity of the entire token economy.
The technical implementation of this vulnerability occurs within the mintToken function where the contract fails to properly validate or constrain integer arithmetic operations when incrementing user balances. When the owner invokes this function with malicious parameters, the integer overflow allows for the manipulation of balance values beyond normal operational limits. The vulnerability exploits the fundamental nature of how Ethereum handles integer operations and the lack of built-in overflow protection in older Solidity versions. This flaw enables attackers to set user balances to extremely high values or even negative values due to the underlying integer overflow behavior. The operational impact extends beyond simple balance manipulation as it can potentially enable theft of funds, creation of unlimited tokens, or disruption of token economics. The vulnerability is particularly dangerous because it operates within the contract's privileged functions, meaning that only the contract owner needs to exploit this flaw to gain unauthorized control over token distributions.
The security implications of CVE-2018-13470 extend to the broader Ethereum ecosystem and token governance models, as it represents a fundamental flaw in how smart contracts handle user balance modifications. This vulnerability can be exploited through the attacker's ability to manipulate the mintToken function parameters, effectively allowing for unauthorized token creation or balance manipulation. The exploitability of this vulnerability is high given that it only requires the contract owner's privileges, which typically include the ability to execute privileged functions. From an attack perspective, this vulnerability aligns with ATT&CK technique T1059.006 for smart contract manipulation and T1496 for data manipulation. The vulnerability's impact on system integrity is severe as it undermines the trust model inherent in blockchain applications, where users expect transparent and accurate balance tracking. This flaw can lead to complete loss of user funds and contract functionality, potentially resulting in the collapse of token-based applications that rely on the affected smart contract.
Mitigation strategies for CVE-2018-13470 should focus on implementing proper input validation and arithmetic overflow protection mechanisms within smart contracts. The recommended approach includes using SafeMath libraries or similar arithmetic libraries that provide overflow protection for all integer operations. Contract developers should implement comprehensive input validation that checks for reasonable balance limits and prevents malicious parameter injection. Additionally, the use of modern Solidity versions that include built-in overflow protection mechanisms should be enforced. Regular security audits and formal verification processes should be implemented to identify similar vulnerabilities before deployment. The contract architecture should also consider implementing access control mechanisms that limit the privileges of the owner function and require multi-signature approval for critical operations. From a defensive standpoint, users should avoid interacting with contracts exhibiting this vulnerability until proper patches are implemented. The vulnerability serves as a reminder of the importance of rigorous security testing in blockchain development and highlights the need for adherence to secure coding practices as outlined in industry standards such as the OWASP Smart Contract Security Verification Standard.