CVE-2018-13735 in ENTER
Summary
by MITRE
The mintToken function of a smart contract implementation for ENTER (ENTR) (Contract Name: EnterToken), 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 • 02/28/2020
The vulnerability identified in CVE-2018-13735 represents a critical integer overflow flaw within the mintToken function of the EnterToken smart contract implementation for the ENTER (ENTR) Ethereum token. This vulnerability stems from improper input validation and arithmetic operations that fail to account for the maximum limits of integer data types, creating a scenario where an attacker can manipulate the token balance of any user account. The flaw exists specifically within the contract's token minting mechanism, which is designed to allow the contract owner to create new tokens and distribute them to users. When the mintToken function processes token creation requests, it performs arithmetic operations without adequate overflow checks, enabling the owner to manipulate the underlying balance storage mechanism through crafted input values.
The technical exploitation of this vulnerability occurs through the manipulation of the mintToken function parameters, particularly when the owner attempts to mint tokens for a target user. The integer overflow allows the owner to set the balance of any user account to an arbitrary value, potentially including extremely large numbers that exceed the normal balance limits of the token system. This type of vulnerability falls under CWE-190, which specifically addresses integer overflow conditions, and more broadly under CWE-682, which covers incorrect arithmetic operations. The vulnerability demonstrates a fundamental flaw in the contract's security design where the owner privilege is not properly constrained, creating a scenario where the contract owner can effectively control all token balances within the system. The attack vector leverages the contract's administrative functions to manipulate the accounting system, bypassing normal token transfer restrictions and potentially enabling unauthorized wealth creation or balance manipulation.
The operational impact of this vulnerability extends beyond simple balance manipulation, as it fundamentally compromises the integrity of the token economy and can lead to significant financial losses for users and the project. An attacker with owner privileges can create unlimited tokens for themselves or other accounts, effectively enabling them to drain the entire token supply or manipulate market dynamics by creating artificial scarcity or abundance. The vulnerability also represents a severe breach of trust in the smart contract system, as users cannot rely on their token balances being accurately maintained. From an attacker's perspective, this vulnerability provides a direct path to financial gain through either the creation of unlimited tokens for personal benefit or by manipulating token distributions to gain unfair advantages in token-based systems. The vulnerability's impact is further amplified by the fact that Ethereum smart contracts execute with immutable logic once deployed, meaning that even if the vulnerability is discovered and patched, any damage already done remains permanent.
Mitigation strategies for this vulnerability require immediate implementation of proper integer overflow protections within the smart contract code, including the use of SafeMath libraries or similar arithmetic validation mechanisms that prevent overflow conditions. The contract should implement comprehensive input validation for all parameters passed to the mintToken function, ensuring that balance calculations remain within valid integer bounds before any modifications are made to user accounts. Additionally, the contract owner privilege should be carefully audited and potentially restricted to prevent unauthorized balance manipulation, with proper access controls and multi-signature requirements for critical operations. Security audits should be conducted to identify similar vulnerabilities in other arithmetic operations within the contract, as integer overflows often occur in multiple locations within complex smart contract systems. The vulnerability also highlights the importance of adhering to established security standards and best practices for smart contract development, including the use of formal verification methods and comprehensive testing procedures to identify potential arithmetic overflow conditions before deployment. Organizations should implement robust monitoring systems to detect unusual balance changes that might indicate exploitation of similar vulnerabilities.