CVE-2018-19830 in Business Alliance Financial Circle
Summary
by MITRE
The UBSexToken() function of a smart contract implementation for Business Alliance Financial Circle (BAFC), an tradable Ethereum ERC20 token, allows attackers to change the owner of the contract, because the function is public (by default) and does not check the caller's identity.
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Analysis
by VulDB Data Team • 01/01/2020
The vulnerability identified as CVE-2018-19830 represents a critical access control flaw within the Business Alliance Financial Circle (BAFC) ERC20 token smart contract implementation. This issue stems from the improper design of the UBSexToken() function which operates with insufficient authorization checks, creating a pathway for unauthorized parties to assume administrative control of the contract. The vulnerability manifests due to the function's public visibility by default, combined with the absence of any caller identity verification mechanisms. This design flaw directly violates fundamental security principles of smart contract development where administrative functions should require explicit authorization from designated parties.
The technical exploitation of this vulnerability occurs through the direct invocation of the UBSexToken() function by any external actor on the Ethereum blockchain. Since the function lacks any form of access control or authentication mechanism, attackers can simply call this function with malicious parameters to transfer ownership of the contract to their own Ethereum address. This represents a classic case of insufficient authorization checking, which is categorized under CWE-284 Access Control Issues. The vulnerability essentially allows for a complete compromise of the contract's administrative privileges, enabling attackers to perform any operation that requires contract ownership including minting new tokens, changing token parameters, or transferring funds.
The operational impact of this vulnerability extends beyond simple ownership transfer, as it fundamentally undermines the security model of the entire BAFC token ecosystem. Once an attacker gains ownership, they can manipulate the token supply, modify distribution parameters, or even drain funds from the contract. This vulnerability creates a significant risk for token holders and investors who rely on the integrity of the smart contract. The attack vector is particularly concerning as it requires no special privileges or complex multi-step processes, making it accessible to any Ethereum user with basic knowledge of smart contract interaction. The vulnerability aligns with ATT&CK technique T1548.001 for Lateral Movement through Privilege Escalation and T1499.004 for Data Destruction through unauthorized access to critical contract functions.
Mitigation strategies for this vulnerability must focus on implementing proper access control mechanisms within the smart contract code. The primary solution involves adding explicit authorization checks to the UBSexToken() function, ensuring that only the current contract owner or designated administrators can invoke this function. This can be achieved through the implementation of require statements that verify the caller's address against a predefined owner address or through more sophisticated access control lists. Additionally, the function should be designed with proper ownership transfer procedures that include multi-signature requirements or time-based delays to prevent immediate unauthorized transfers. The implementation should follow security best practices outlined in the Ethereum Smart Contract Security Best Practices document and align with the OWASP Smart Contract Security Verification Standard. Regular security audits and formal verification of smart contract code should be conducted to identify similar vulnerabilities across the entire contract implementation. The vulnerability demonstrates the critical importance of proper access control design in blockchain applications where a single flaw can result in complete loss of control over the contract and associated assets.