FuturXE Ethereum ERC20 Token transferFrom Smart Contract Logic input validation

Summaryinfo

A vulnerability has been found in FuturXE and classified as critical. Impacted is the function transferFrom of the component Ethereum ERC20 Token Handler. This manipulation as part of Smart Contract causes input validation (Logic). This vulnerability is handled as CVE-2018-12025. The attack can be initiated remotely. There is not any exploit available.

Detailsinfo

A vulnerability was found in FuturXE (the affected version unknown). It has been declared as critical. Affected by this vulnerability is the function transferFrom of the component Ethereum ERC20 Token Handler. The manipulation as part of a Smart Contract leads to a input validation vulnerability (Logic). The CWE definition for the vulnerability is CWE-20. The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly. As an impact it is known to affect confidentiality, integrity, and availability. The summary by CVE is:

The transferFrom function of a smart contract implementation for FuturXE (FXE), an Ethereum ERC20 token, allows attackers to accomplish an unauthorized transfer of digital assets because of a logic error. The developer messed up with the boolean judgment - if the input value is smaller than or equal to allowed value, the transfer session would stop execution by returning false. This makes no sense, because the transferFrom() function should require the transferring value to not exceed the allowed value in the first place. Suppose this function asks for the allowed value to be smaller than the input. Then, the attacker could easily ignore the allowance: after this condition, the `allowed[from][msg.sender] -= value;` would cause an underflow because the allowed part is smaller than the value. The attacker could transfer any amount of FuturXe tokens of any accounts to an appointed account (the `_to` address) because the allowed value is initialized to 0, and the attacker could bypass this restriction even without the victim's private key.

The bug was discovered 06/06/2018. The weakness was released 06/11/2018 (Website). It is possible to read the advisory at medium.com. This vulnerability is known as CVE-2018-12025 since 06/07/2018. The exploitation appears to be easy. The attack can be launched remotely. The exploitation doesn't need any form of authentication. Technical details of the vulnerability are known, but there is no available exploit.

The vulnerability was handled as a non-public zero-day exploit for at least 5 days. During that time the estimated underground price was around $0-$5k.

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

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• FuturXE

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CPE 2.2info

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