CVE-2018-13768 in Ztoken
Summary
by MITRE
The mintToken function of a smart contract implementation for ZToken, 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.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 03/03/2020
The vulnerability described in CVE-2018-13768 represents a critical integer overflow flaw within the mintToken function of the ZToken smart contract implementation on the Ethereum blockchain. This vulnerability stems from inadequate input validation and arithmetic overflow handling within the contract's code, specifically affecting the token minting mechanism that allows contract owners to create new tokens. The flaw manifests when the contract attempts to increment token balances without proper bounds checking, creating a scenario where arithmetic operations can exceed the maximum value representable by the underlying data type.
The technical implementation of this vulnerability places the smart contract at significant risk of being exploited through unauthorized balance manipulation. When the mintToken function processes token creation requests, it fails to validate whether the resulting balance would exceed the maximum integer value for the data type being used. This allows an attacker with owner privileges to craft malicious inputs that cause integer overflow conditions, effectively manipulating user balances to arbitrary values. The vulnerability is classified under CWE-190 as an integer overflow or wraparound, which occurs when a computation produces a result that exceeds the maximum value that can be stored in the designated data type.
The operational impact of this vulnerability extends beyond simple balance manipulation to potentially compromise the entire token economy and user trust in the system. An attacker with owner access can increase any user's balance to extremely high values, potentially leading to token supply inflation or even complete system compromise. The vulnerability also opens pathways for various attack vectors including but not limited to front-running attacks, balance manipulation for fraudulent transactions, and potential denial of service conditions where legitimate users cannot perform normal operations due to manipulated state values. This type of vulnerability directly impacts the integrity and availability of the smart contract system, violating fundamental security principles of blockchain applications.
Mitigation strategies for this vulnerability require immediate code review and patching of the smart contract implementation to address the integer overflow conditions. The recommended approach involves implementing proper bounds checking and overflow protection mechanisms such as using safe math libraries, validating all input parameters, and ensuring arithmetic operations cannot exceed maximum data type limits. Organizations should also implement comprehensive testing procedures including formal verification and automated security scanning to identify similar vulnerabilities in other smart contracts. The vulnerability demonstrates the critical importance of following secure coding practices in blockchain development and aligns with ATT&CK technique T1548.005 for privilege escalation through smart contract manipulation. Additionally, the incident highlights the necessity of implementing proper access controls and regular security audits to prevent unauthorized modifications to smart contract code that could enable such exploitations.