CVE-2018-13564 in GATcoin
Summary
by MITRE
The mintToken function of a smart contract implementation for GATcoin, 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 • 02/27/2020
The vulnerability identified as CVE-2018-13564 represents a critical integer overflow flaw within the mintToken function of GATcoin's Ethereum smart contract implementation. This vulnerability stems from improper input validation and arithmetic operations that fail to account for boundary conditions in the Ethereum blockchain's uint256 data type. The flaw allows the contract owner to manipulate token balances through direct manipulation of the mintToken function, creating a scenario where arbitrary user balances can be set to any desired value. The vulnerability is particularly dangerous because it directly impacts the fundamental integrity of the token economy and can be exploited to create unlimited tokens or manipulate user holdings without detection.
The technical implementation of this vulnerability occurs when the mintToken function performs arithmetic operations without proper overflow checks, specifically when adding new tokens to existing balances. In Ethereum smart contracts, integer overflows occur when arithmetic operations exceed the maximum value that can be stored in a data type, causing the value to wrap around to zero or negative values. The GATcoin implementation fails to validate that the addition of new tokens to existing balances will not exceed the maximum uint256 value, creating a condition where malicious actors can exploit this flaw to manipulate balances. This vulnerability aligns with CWE-190, Integer Overflow or Wraparound, which specifically addresses issues where integer arithmetic operations produce results that exceed the maximum representable value for the data type. The flaw demonstrates poor defensive programming practices that violate fundamental smart contract security principles.
The operational impact of this vulnerability extends beyond simple balance manipulation to encompass complete financial control and potential systemic risks within the GATcoin ecosystem. An attacker with access to the contract owner privileges can create unlimited tokens, manipulate user balances to favor specific accounts, or even drain the entire token supply through carefully crafted overflow conditions. The vulnerability affects all users of the GATcoin token since any user's balance can be manipulated, potentially leading to market manipulation, loss of user trust, and complete devaluation of the token. The exploitability of this vulnerability is high given that it requires only owner privileges and can be executed through direct function calls to the mintToken function. This type of vulnerability directly impacts the security and integrity of the blockchain-based financial system, as it undermines the core principle that token balances should be immutable and accurately reflected.
Mitigation strategies for CVE-2018-13564 require immediate implementation of proper input validation and arithmetic boundary checks within the smart contract code. The most effective solution involves adding explicit overflow checks using require statements before any arithmetic operations in the mintToken function, ensuring that additions to balances do not exceed the maximum uint256 value. Smart contract developers should implement comprehensive testing including boundary condition testing and formal verification techniques to identify similar vulnerabilities. The fix should also incorporate proper access control mechanisms to prevent unauthorized manipulation of token balances, aligning with ATT&CK technique T1548.001 for privilege escalation and T1078.004 for valid accounts. Additionally, the contract should be audited for similar integer overflow vulnerabilities in other functions, particularly those involving arithmetic operations. Regular security audits and adherence to established smart contract security frameworks such as the Solidity security guidelines are essential to prevent recurrence of such vulnerabilities in future implementations.