CVE-2018-13474 in FansChainToken
Summary
by MITRE
The mintToken function of a smart contract implementation for FansChainToken, 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 • 02/26/2020
The mintToken function in the FansChainToken smart contract implementation on the Ethereum blockchain contains a critical integer overflow vulnerability that fundamentally compromises the contract's integrity and security model. This vulnerability exists within the token's core functionality where the owner can manipulate user balances through improper integer handling during token minting operations. The flaw allows an attacker with owner privileges to arbitrarily set any user's token balance to any desired value, effectively bypassing all normal tokenomics and distribution mechanisms. The vulnerability stems from the contract's failure to properly validate or constrain integer values during arithmetic operations, creating an exploitable condition that can be leveraged to manipulate the entire token economy.
The technical exploitation of this vulnerability occurs when the mintToken function processes token minting operations without proper overflow checks or value validation. In Ethereum smart contracts, integer overflows typically occur when arithmetic operations exceed the maximum value that can be stored in a given data type, causing the value to wrap around to zero or negative values. This specific implementation lacks proper bounds checking and input validation mechanisms that would normally prevent such conditions. The vulnerability directly maps to CWE-190, which describes integer overflow and underflow conditions, and represents a critical weakness in the contract's mathematical operations. When an attacker invokes the mintToken function with malicious parameters, the integer overflow allows them to manipulate the balance storage mechanism to achieve arbitrary balance assignments, effectively granting them control over any user's token holdings.
The operational impact of this vulnerability extends far beyond simple balance manipulation, as it fundamentally undermines the trust model and economic security of the FansChainToken ecosystem. An attacker with owner access can create unlimited tokens for themselves while simultaneously setting other users' balances to zero or negative values, leading to potential total loss of funds for token holders. This vulnerability enables several attack vectors including but not limited to account manipulation, potential theft of funds, and disruption of the token's intended distribution model. The exploitability of this condition is particularly dangerous because it requires only owner privileges, which are typically limited to a small set of trusted individuals or entities. The vulnerability can be leveraged to create artificial scarcity, manipulate token prices, or completely drain user accounts, making it a severe threat to the token's economic stability and user confidence. This type of vulnerability aligns with ATT&CK technique T1499.004, which covers network denial of service through manipulation of resource availability.
Mitigation strategies for this vulnerability require immediate implementation of comprehensive input validation and integer overflow protection mechanisms within the smart contract code. The primary remediation involves adding proper bounds checking and overflow detection before any arithmetic operations occur during token minting processes. Developers should implement safe math libraries or utilize established secure coding practices that prevent integer overflows through explicit validation of input parameters. The contract should enforce maximum balance limits and validate all user inputs to ensure they fall within acceptable ranges. Additionally, the owner privileges should be carefully audited and potentially restricted to prevent unauthorized manipulation of user balances. Regular security audits and formal verification of smart contract code are essential to prevent similar vulnerabilities from being introduced in future updates. The remediation process should also include a thorough review of all functions that handle token balances and arithmetic operations to ensure comprehensive protection against integer overflow conditions across the entire contract implementation.