CVE-2018-13710 in Mjolnir
Summary
by MITRE
The mintToken function of a smart contract implementation for Mjolnir, 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 as CVE-2018-13710 resides within the mintToken function of a smart contract implementation for the Mjolnir Ethereum token, representing a critical integer overflow flaw that fundamentally compromises the contract's integrity and security model. This vulnerability specifically affects the token's ability to manage user balances through the minting process, creating a pathway for malicious actors to manipulate token distributions and potentially gain unauthorized control over the token ecosystem.
The technical flaw manifests as an integer overflow in the mintToken function where the contract fails to properly validate or constrain the amount parameter during token creation. When an owner invokes this function with a large value, the arithmetic operations involved in updating user balances can exceed the maximum limit for the data type being used, causing the value to wrap around to an unexpectedly small or negative number. This overflow behavior occurs due to the lack of proper input validation and overflow protection mechanisms within the smart contract code, which is a common pattern in Solidity implementations that fail to implement comprehensive mathematical operation safeguards.
The operational impact of this vulnerability extends far beyond simple balance manipulation, as it allows the contract owner to arbitrarily set any user's balance to any desired value, potentially enabling unauthorized token distribution, account manipulation, and exploitation of the token economy. An attacker could leverage this vulnerability to inflate their own balance, drain other users' balances, or create artificial scarcity by setting specific balances to zero. This flaw directly undermines the fundamental principles of blockchain tokenomics and trustless systems, as it allows a single privileged account to subvert the intended distribution and governance mechanisms of the token contract.
The vulnerability aligns with CWE-190, Integer Overflow or Wraparound, which specifically addresses the dangerous behavior of integer arithmetic operations that exceed their maximum representable value. From an attack perspective, this issue maps to the ATT&CK technique T1548.001, which involves privilege escalation through the manipulation of system resources. The exploitability of this vulnerability is enhanced by the fact that it requires no special privileges beyond contract ownership, making it particularly dangerous as it allows for direct manipulation of the token supply without any additional attack vectors. Organizations and developers should implement rigorous input validation, utilize safe math libraries, and conduct comprehensive smart contract audits to prevent such arithmetic overflow vulnerabilities from compromising blockchain-based systems.
Mitigation strategies for this vulnerability should include implementing proper integer overflow checks using libraries such as OpenZeppelin's SafeMath, validating all input parameters before arithmetic operations, and ensuring that balance updates are constrained within reasonable limits. Additionally, smart contracts should employ comprehensive testing procedures including fuzz testing and formal verification to identify potential overflow scenarios. The contract should also implement proper access controls and audit trails to monitor any unusual balance modifications, while developers should adopt defensive programming practices that assume all external inputs may be malicious and validate accordingly.