CVE-2018-13605 in Extreme Coin
Summary
by MITRE
The mintToken function of a smart contract implementation for Extreme Coin (XT) (Contract Name: ExtremeToken), 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 in CVE-2018-13605 affects the Extreme Coin (XT) smart contract implementation on the Ethereum blockchain, specifically targeting the mintToken function within the ExtremeToken contract. This flaw represents a critical security weakness that directly impacts the contract's integrity and the underlying token economy. The vulnerability stems from improper input validation and arithmetic handling within the smart contract code, creating a scenario where the contract owner can manipulate user balances arbitrarily. Such a flaw fundamentally undermines the trustless nature of blockchain-based systems and represents a severe deviation from expected contract behavior.
The technical flaw manifests as an integer overflow condition within the mintToken function, which occurs when the contract attempts to increment token balances without proper bounds checking. This vulnerability falls under CWE-190, Integer Overflow or Wraparound, and specifically demonstrates how insufficient validation of numeric inputs can lead to unintended contract states. When the mintToken function processes token creation requests, it fails to validate whether the resulting balance would exceed the maximum value that can be represented by the data type used for balance storage. This allows an attacker with contract ownership privileges to specify any arbitrary balance value, effectively enabling them to mint unlimited tokens for themselves or other users.
The operational impact of this vulnerability extends far beyond simple balance manipulation, as it creates a fundamental threat to the token's economic model and user trust. Contract owners can exploit this flaw to create infinite token supply for malicious purposes, potentially leading to severe dilution of token value and complete loss of user funds. The vulnerability enables several attack vectors including unauthorized token generation, balance manipulation, and potential theft of funds from other users' accounts. From an attack perspective, this represents a privilege escalation vulnerability that allows the owner to bypass normal transactional controls and directly modify account balances. The attack surface is particularly concerning as it operates at the core contract level, making it difficult to detect and remediate without complete contract redeployment.
Mitigation strategies for this vulnerability must address both immediate remediation and long-term security practices. The primary solution involves implementing proper integer overflow protection through bounds checking and using safe arithmetic operations in smart contract development. Developers should utilize established libraries such as OpenZeppelin's SafeMath or similar libraries that provide overflow protection mechanisms. Additionally, contract owners should implement comprehensive testing procedures including formal verification and security audits to identify similar vulnerabilities before deployment. The remediation process requires careful consideration of the existing token distribution and may necessitate a complete contract redeployment to ensure all users' balances remain intact while eliminating the exploitable vulnerability. Organizations should also establish secure development practices and adhere to industry standards like the Ethereum Smart Contract Best Practices guidelines to prevent similar issues in future implementations.
This vulnerability demonstrates the critical importance of proper input validation and arithmetic handling in smart contract development, aligning with ATT&CK technique T1059.006 for smart contract exploitation and T1496 for data manipulation. The flaw represents a direct violation of the principle of least privilege, where contract ownership should not grant unlimited control over user funds. Security practitioners should consider this vulnerability as part of broader smart contract security frameworks and implement comprehensive monitoring to detect unauthorized balance modifications. The incident underscores the need for continuous security assessment and the adoption of defensive programming practices in blockchain environments.