CVE-2018-13656 in Sample Token
Summary
by MITRE
The mintToken function of a smart contract implementation for Sample Token (STK) (Contract Name: cashBackMintable), 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-2018-13656 resides within the mintToken function of a smart contract implementation for the Sample Token (STK) known as cashBackMintable on the Ethereum blockchain. This flaw represents a critical integer overflow condition that fundamentally compromises the contract's integrity and security model. The vulnerability manifests when the owner of the contract invokes the mintToken function, enabling them to manipulate user balances beyond normal operational parameters. The integer overflow occurs due to insufficient input validation and boundary checking within the function's implementation, creating a pathway for arbitrary balance manipulation.
The technical exploitation of this vulnerability stems from the contract's failure to properly validate integer values during the token minting process. When the owner calls the mintToken function, the contract does not adequately check for potential overflow conditions that could occur when adding new token values to existing user balances. This oversight allows the contract owner to specify any arbitrary balance value for target users, effectively bypassing normal token distribution mechanisms and creating a scenario where malicious actors could manipulate token distributions. The vulnerability operates at the core of the contract's accounting system, where the balance of any user can be set to an arbitrary value without proper authorization or validation checks.
Operationally, this vulnerability presents severe implications for the token ecosystem and its participants. The ability for a contract owner to arbitrarily set user balances creates a fundamental trust violation within the token system, potentially enabling unauthorized wealth redistribution or manipulation of token economics. Attackers could exploit this vulnerability to inflate their own balances, manipulate token distribution events, or create artificial market conditions that benefit malicious actors. The impact extends beyond individual user accounts to potentially destabilize the entire token economy, as the integrity of the token supply and user balance tracking becomes compromised. This vulnerability essentially grants the contract owner unlimited control over token distribution, undermining the decentralized and trustless principles that smart contracts are designed to uphold.
Mitigation strategies for CVE-2018-13656 should focus on implementing comprehensive input validation and boundary checking within the mintToken function. The contract implementation must incorporate proper integer overflow protection mechanisms such as using safe math libraries or implementing explicit overflow checks before any arithmetic operations. Additionally, access controls should be strengthened to ensure that only authorized entities can invoke mintToken functions, and all balance modifications should be subject to proper audit trails. The fix should align with industry standards including CWE-190 for integer overflow conditions and should be consistent with ATT&CK framework techniques related to smart contract exploitation. Regular security audits and formal verification of smart contract code should be implemented to prevent similar vulnerabilities from emerging in future contract deployments. The remediation process must also include thorough testing of boundary conditions and comprehensive validation of all user inputs to ensure that the contract maintains its intended behavior under all operational scenarios.