CVE-2018-13209 in Nectar
Summary
by MITRE
The sell function of a smart contract implementation for Nectar (NCTR), an Ethereum token, has an integer overflow in which "amount * sellPrice" can be zero, consequently reducing a seller's assets.
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Analysis
by VulDB Data Team • 02/25/2020
The vulnerability identified in CVE-2018-13209 affects the Nectar (NCTR) smart contract implementation on the Ethereum blockchain, specifically within the sell function of the token contract. This represents a critical integer overflow flaw that fundamentally compromises the contract's financial integrity and asset management capabilities. The vulnerability arises from improper input validation and arithmetic operation handling within the smart contract's sell function, creating a scenario where mathematical operations can produce unexpected results due to insufficient boundary checks.
The technical flaw manifests when the sell function processes transactions involving token sales, where the multiplication operation "amount * sellPrice" can result in zero even when both operands are non-zero. This occurs because the smart contract fails to properly validate the multiplication result against potential overflow conditions or zero values that could arise from the arithmetic operation. The vulnerability is classified as an integer overflow according to CWE-190, which specifically addresses issues related to integer arithmetic operations producing values outside the valid range for the data type. This particular implementation flaw falls under the broader category of CWE-191, which deals with integer underflow and overflow conditions, and more specifically aligns with CWE-194, which addresses signed integer overflow with negative values.
The operational impact of this vulnerability is severe and directly affects the financial security of users who hold NCTR tokens. When a seller attempts to sell their tokens, the contract incorrectly calculates the value of the transaction, potentially resulting in zero value being credited to the seller's account despite valid token amounts being offered for sale. This creates a situation where sellers lose their assets without receiving any compensation, effectively draining their token holdings. The vulnerability allows for unauthorized asset reduction through manipulation of the sell function parameters, creating a vector for financial loss that could potentially be exploited repeatedly by malicious actors. The flaw also undermines trust in the token's smart contract implementation and could have broader implications for the entire Nectar ecosystem.
From a cybersecurity perspective, this vulnerability demonstrates the critical importance of proper smart contract development practices and thorough security auditing. The issue aligns with ATT&CK technique T1587.001, which involves developing capabilities for financial loss through exploitation of smart contract vulnerabilities. The vulnerability could be exploited by attackers who identify the specific conditions under which the integer overflow occurs, potentially leading to systematic asset theft from multiple users. Organizations and developers should implement comprehensive input validation, utilize safe arithmetic libraries, and conduct thorough testing including edge case scenarios to prevent similar vulnerabilities. The incident highlights the need for adherence to secure coding practices such as those outlined in the Ethereum Smart Contract Security Best Practices and emphasizes the importance of formal verification methods to detect mathematical operation flaws before deployment on the blockchain. Proper mitigation would involve patching the smart contract to include overflow checks, implementing proper validation of multiplication results, and ensuring that all arithmetic operations are performed within safe boundaries to prevent the zero-value calculation that leads to asset loss.