CVE-2018-13539 in Bcxss
Summary
by MITRE
The mintToken function of a smart contract implementation for Bcxss, 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-2018-13539 represents a critical integer overflow flaw within the mintToken function of the Bcxss Ethereum token smart contract implementation. This vulnerability resides in the contract's token minting mechanism where the owner can manipulate user balances through improper integer handling. The flaw allows for arbitrary balance manipulation by exploiting the lack of proper overflow checks during arithmetic operations. When the mintToken function processes token minting requests, it fails to validate whether the resulting balance would exceed the maximum value that can be represented by the integer data type, creating a condition where overflow occurs and produces unexpected results.
The technical execution of this vulnerability stems from the absence of input validation and overflow protection mechanisms within the smart contract code. The integer overflow occurs when the contract attempts to increment a user's balance beyond the maximum representable value for the data type, causing the value to wrap around to zero or a negative number. This behavior directly violates the expected mathematical properties of integer arithmetic and creates a path for unauthorized balance manipulation. The vulnerability specifically affects the Ethereum blockchain environment where smart contracts execute with deterministic behavior, making such flaws particularly dangerous as they can be exploited systematically by contract owners or attackers with access to owner privileges.
The operational impact of this vulnerability extends beyond simple balance manipulation to potentially compromise the entire token economy and user trust in the Bcxss token ecosystem. An attacker with owner privileges can artificially inflate user balances to arbitrary values, potentially creating an inflationary effect that undermines token scarcity and value proposition. The vulnerability also enables potential denial of service scenarios where malicious actors could set user balances to zero or extremely high values, disrupting normal token operations and user transactions. This type of vulnerability directly impacts the core principles of blockchain tokenomics and can lead to financial losses for users who hold the affected token.
Security mitigations for this vulnerability require immediate implementation of proper integer overflow protection mechanisms within the smart contract code. The recommended approach involves adding explicit overflow checks before any arithmetic operations that could potentially exceed data type limits, utilizing safe arithmetic libraries or compiler features that provide automatic overflow detection. The contract owner should implement proper access controls and audit trails to monitor token minting activities, ensuring that only legitimate minting operations occur. Additionally, the vulnerability aligns with CWE-191, which specifically addresses integer underflow and overflow conditions, and maps to ATT&CK technique T1210 for exploiting weaknesses in smart contracts. Regular security audits and formal verification of smart contract code should be implemented to prevent similar vulnerabilities in future deployments, as this flaw demonstrates the critical importance of proper input validation in blockchain applications where financial assets are at stake.