CVE-2023-37902

ecrecover can return undefined data if signature does not verify

Workarounds

Is there a way for users to fix or remediate the vulnerability without upgrading?

References

Are there any links users can visit to find out more?

the ecrecover precompile does not fill the output buffer if the signature does not verify, see https://github.com/ethereum/go-ethereum/blob/b058cf454b3bdc7e770e2b3cec83a0bcb48f55ee/core/vm/contracts.go#L188. however, the ecrecover builtin will still return whatever is at memory location 0.

this means that the if the compiler has been convinced to write to the 0 memory location with specially crafted data (generally, this can happen with a hashmap access or immutable read) just before the ecrecover, a signature check might pass on an invalid signature.

A contract search was performed. Most uses of ecrecover are used for erc2612-style permit implementations, which typically look like:

    assert _owner != empty(address)
    assert block.timestamp <= _deadline
                  
    nonce: uint256 = self.nonces[_owner]
    digest: bytes32 = keccak256(
        concat(   
            b"\x19\x01",
            self.DOMAIN_SEPARATOR,
            keccak256(_abi_encode(PERMIT_TYPEHASH, _owner, _spender, _value, nonce, _deadline))
        )         
    )             
    assert ecrecover(digest, convert(_v, uint256), convert(_r, uint256), convert(_s, uint256)) == _owner

in this case, the immutable PERMIT_TYPEHASH is loaded into ecrecover's output buffer right before ecrecover(), and so the output of ecrecover() here when the signature is invalid will be the value of PERMIT_TYPEHASH. in this case, since PERMIT_TYPEHASH is not a valid address, it will never compare == to _owner, and so the behaviour is exactly the same as if ecrecover() returned 0 in this case.

in general, a contract could have unexpected behavior (i.e. mistakenly pass this style of signature check) if an immutable representing a real address (ex. OWNER) was read right before the ecrecover operation.

CVE-2023-37902 has a CVSS score of 5.3 (Medium). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (0.3.10); upgrading removes the vulnerable code path.

Kodem intelligence

Already deployed Kodem?

v0.3.10 (with 019a37ab98ff53f04fecfadf602b6cd5ac748f7f and #3586)

1. What is CVE-2023-37902? CVE-2023-37902 is a medium-severity security vulnerability in vyper (pip), affecting versions < 0.3.10. It is fixed in 0.3.10.
2. How severe is CVE-2023-37902? CVE-2023-37902 has a CVSS score of 5.3 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of vyper are affected by CVE-2023-37902? vyper (pip) versions < 0.3.10 is affected.
4. Is there a fix for CVE-2023-37902? Yes. CVE-2023-37902 is fixed in 0.3.10. Upgrade to this version or later.
5. Is CVE-2023-37902 exploitable, and should I be worried? Whether CVE-2023-37902 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2023-37902 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2023-37902? Upgrade vyper to 0.3.10 or later.

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