CVE-2018-18665 in Nexxus NXX
Summary
by MITRE
The mintToken function of Nexxus (NXX) aka NexxusToken, 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 • 04/24/2020
The vulnerability identified as CVE-2018-18665 resides within the mintToken function of the Nexxus (NXX) token smart contract deployed on the Ethereum blockchain. This represents a critical security flaw that fundamentally undermines the integrity of the token's supply mechanism and user balance management. The vulnerability manifests as an integer overflow condition that occurs when processing token minting operations, creating a scenario where the contract owner can manipulate user balances beyond normal operational parameters.
The technical flaw stems from improper input validation and arithmetic handling within the mintToken function implementation. When the contract processes token minting requests, it fails to adequately check for integer overflow conditions before performing arithmetic operations on balance values. This allows an attacker with ownership privileges to manipulate the token supply by setting arbitrary user balances to any value they choose, effectively bypassing the normal token distribution and accounting mechanisms. The vulnerability specifically affects the uint256 data type handling within the smart contract, where operations can exceed maximum representable values and wrap around to zero or negative values, creating unpredictable behavior in balance calculations.
The operational impact of this vulnerability extends beyond simple balance manipulation to encompass potential financial loss and contract integrity compromise. An attacker with access to the contract owner privileges can inflate user balances to excessive levels, potentially causing the token supply to become artificially inflated or creating situations where user accounts contain impossible balance values. This vulnerability enables malicious actors to exploit the token economy by creating artificial wealth for specific addresses or manipulating the total supply calculations that might be used for governance voting rights or other token-based mechanisms. The implications are particularly severe in decentralized finance applications where token balances directly affect liquidity, collateral values, and user trust in the system's integrity.
Mitigation strategies for this vulnerability require immediate contract hardening and comprehensive security auditing of all smart contract functions. The primary remediation involves implementing proper integer overflow checks using modern solidity versions that include built-in overflow protection mechanisms or explicit validation routines before arithmetic operations. Developers should employ techniques such as using require statements to validate input parameters, implementing bounded arithmetic operations, and utilizing established libraries like OpenZeppelin's SafeMath for mathematical operations. This vulnerability aligns with CWE-190, Integer Overflow or Wraparound, and represents a common pattern in smart contract development where insufficient input validation leads to critical security flaws. Organizations should also implement multi-signature ownership models, regular security audits, and comprehensive testing procedures including formal verification to prevent similar issues in future deployments. The ATT&CK framework categorizes this vulnerability under privilege escalation techniques where attackers leverage administrative functions to manipulate system state, emphasizing the importance of proper access controls and function-level security checks in blockchain applications.