CVE-2018-13189 in Unolabo
Summary
by MITRE
The mint function of a smart contract implementation for Unolabo (UNLB), 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 • 02/25/2020
The vulnerability identified in CVE-2018-13189 affects the Unolabo (UNLB) Ethereum token smart contract implementation, specifically targeting the mint function that enables token creation and distribution. This flaw represents a critical security weakness in the contract's arithmetic operations that directly impacts the token's integrity and user fund safety. The vulnerability stems from improper handling of integer values during the minting process, creating opportunities for malicious actors to manipulate token balances within the system.
The technical flaw manifests as an integer overflow condition within the mint function where the contract fails to properly validate or constrain input parameters before performing arithmetic operations. When the owner invokes the mint function with specific parameters, the contract's internal calculations exceed the maximum value that can be represented by the integer data type, causing the value to wrap around to an unexpected lower value. This overflow behavior allows the contract owner to manipulate the target user's balance to any desired amount, effectively enabling arbitrary balance manipulation. The vulnerability is classified as a CWE-191 Integer Underflow/Overflow, specifically involving unsigned integer overflow conditions that can be exploited for financial gain.
The operational impact of this vulnerability extends beyond simple balance manipulation to potentially compromise the entire token ecosystem and user trust. An attacker with access to the contract owner account can instantly create unlimited tokens for themselves or other users, leading to severe dilution of token value and potential financial losses for legitimate holders. The vulnerability also creates opportunities for denial of service attacks where malicious actors could manipulate balances to prevent legitimate transactions or create artificial scarcity. This type of vulnerability directly impacts the security posture of the Ethereum blockchain ecosystem and demonstrates the critical importance of proper input validation in smart contract development.
Mitigation strategies for this vulnerability require immediate contract redeployment with proper integer overflow protection mechanisms. The fix involves implementing comprehensive input validation checks that verify all parameters before arithmetic operations, utilizing safe math libraries that automatically detect and prevent overflow conditions, and ensuring proper bounds checking on all user-supplied values. Security practitioners should implement the principle of least privilege by restricting mint function access to verified addresses only and consider implementing multi-signature requirements for critical contract operations. Additionally, the vulnerability highlights the necessity for comprehensive smart contract auditing and formal verification processes to identify similar issues before deployment. This case study aligns with ATT&CK technique T1548.001 for privilege escalation and demonstrates the importance of defensive programming practices in blockchain environments where financial assets are at stake. Organizations should adopt security frameworks such as the OpenZeppelin security guidelines and implement continuous monitoring of contract interactions to detect anomalous behavior patterns that may indicate exploitation attempts.