CVE-2018-13767 in Cornerstone
Summary
by MITRE
The mintToken function of a smart contract implementation for Cornerstone, 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 • 03/03/2020
The vulnerability identified in CVE-2018-13767 represents a critical integer overflow flaw within the mintToken function of a Cornerstone Ethereum token smart contract implementation. This vulnerability stems from inadequate input validation and arithmetic overflow handling in the smart contract code, creating a scenario where the contract owner can manipulate user balances arbitrarily. The flaw exists at the core of the token's issuance mechanism, where the mintToken function fails to properly validate or constrain the values being processed during token creation and distribution.
The technical exploitation of this vulnerability occurs through the manipulation of integer variables within the mintToken function, specifically when handling large numerical values that exceed the maximum limits of the data types used. This creates an overflow condition where the arithmetic operation wraps around to a smaller value, allowing the contract owner to bypass normal balance limitations and set any user's token balance to an arbitrary value. The vulnerability maps directly to CWE-190, Integer Overflow or Wraparound, which is classified as a fundamental weakness in software design that allows attackers to manipulate integer values beyond their intended range. The overflow condition typically manifests when the contract attempts to increment a user's balance beyond the maximum value that can be represented by the underlying data type, causing the value to wrap around to zero or another unexpected value.
The operational impact of this vulnerability is severe and far-reaching within the Ethereum ecosystem, as it provides the contract owner with unprecedented control over token distribution and user balances. An attacker with access to the owner account can manipulate token balances to create unlimited tokens, effectively undermining the token's economic model and potentially causing significant financial loss to other users. This vulnerability also creates a pathway for potential theft of funds, as the attacker can set their own balance to extremely high values while simultaneously reducing other users' balances to zero. The implications extend beyond immediate financial harm to include trust erosion in the token ecosystem and potential regulatory concerns regarding unauthorized manipulation of token distributions.
Mitigation strategies for this vulnerability require immediate code remediation through proper input validation and overflow protection mechanisms. Smart contract developers must implement explicit checks to prevent integer overflows by validating all input parameters and using safe arithmetic operations such as those provided by libraries like OpenZeppelin's SafeMath. The contract owner should also implement proper access controls and audit trails to monitor any balance modifications, while considering the implementation of time locks or multi-signature requirements for critical operations. This vulnerability highlights the importance of adhering to security best practices in smart contract development, including the principles outlined in the OWASP Smart Contract Security Verification Standard, which emphasizes the need for comprehensive input validation and proper error handling. Additionally, the ATT&CK framework for smart contracts would categorize this vulnerability under the T1548.001 technique for privilege escalation through overflow conditions, making it a critical target for security audits and penetration testing in blockchain environments.