3.11 ecrecover

This security pitfall is related to the use of the ecrecover primitive in EVM and supported by Solidity.

The specific pitfall is that it is susceptible to what is known as signature malleability or non-unique signatures. Remember that elliptic curve signatures in Ethereum have three components v, r and s. The ecrecover function takes in a message hash the signature associated with that message hash and returns the Ethereum address that corresponds to the private key that was used to create that signature.

In the context of this pitfall, if an attacker has access to one of these signatures, then they can create a second valid signature without having access to the private key to generate that signature.

This is because of the specific range that the s value or the s component of that signature can be in it can be in an upper range or a lower range and both ranges are allowed by this primitive which results in the malleability.

This depending on the logic of the smart contract, the context in which it is using these signatures can result in replay attacks, so the mitigation is to check that the s component is only in the lower range and not in the higher range, this mitigation is enforced in OpenZeppelin's ECDSA library which is the recommended best practice.