CVE-2018-12025
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedThe 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.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceThe FuturXE (FXE) ERC20 token has a logic error in the transferFrom function where the allowance check is inverted - it returns false when the input value is smaller than or equal to the allowed amount, when it should only allow transfers when value is less than or equal to allowed. Combined with an underflow in the subtraction of allowed[from][msg.sender] -= value, attackers can transfer any amount of tokens from any account because allowed is initialized to 0.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE dataall versionsCVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- High
- Availability
- None
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Locate the FuturXE token contract deploymentSearch blockchain explorers for the FuturXE (FXE) token contract address. Common sources include the token's official website, listings on cryptocurrency tracking platforms, or token discovery databases.Affected if You have a deployed FuturXE contract and can interact with it or view its code.
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Obtain the contract source code or verify the bytecodeIf the contract is verified on block explorers like Etherscan, view the source code directly. If not verified, you may need to decompile the bytecode or interact with the contract through read functions.Affected if Source code is available for inspection of the transferFrom function logic.
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Inspect the transferFrom function for inverted allowance logicExamine the transferFrom function code. Look for a condition that returns false (or reverts) when the transfer value is less than or equal to the allowed amount. The vulnerable code will incorrectly reject valid transfers where value <= allowed.Affected if The transferFrom function contains an inverted boolean check that rejects transfers when value <= allowed (should allow) instead of only rejecting when value > allowed.
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Verify the subtraction uses SafeMathCheck if the line 'allowed[from][msg.sender] -= value' uses SafeMath sub() function or equivalent overflow protection. If it uses plain Solidity arithmetic (-=), the underflow vulnerability exists.Affected if The allowance subtraction uses plain arithmetic without SafeMath, allowing underflow when value exceeds allowed.
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Test the vulnerability with a read call if possibleCall the contract's allowance function for any address to check the allowed value. Since allowed is initialized to 0, attempting a transferFrom with any value should either incorrectly pass the inverted check or cause unexpected behavior.Affected if The contract exhibits the described behavior where transfers fail incorrectly or succeed when they should not.
The environment is affected if the FuturXE token contract is deployed and its transferFrom function contains the inverted allowance check combined with non-SafeMath subtraction.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
From vendor dataFix the boolean condition in transferFrom to properly check if value exceeds allowance, and use SafeMath library for arithmetic operations to prevent underflow/overflow vulnerabilities.
- Consultation3.0 h
- Implementation2.0 h
- Testing6.0 h
- Review / QA3.0 h
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Free · runs locallyCheck whether your project pulls in CVE-2018-12025 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2018-12025 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
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