CVE-2023-37902: Vyper's ecrecover can return undefined data if signature does not verify

Impact 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:

vyper assert owner != empty(address) assert block.timestamp <= deadline nonce: uint256 = self.nonces[owner] digest: bytes32 = keccak256( concat( b"\x19\x01", self.DOMAINSEPARATOR, keccak256(abiencode(PERMITTYPEHASH, owner, spender, value, nonce, deadline)) ) ) assert ecrecover(digest, convert(v, uint256), convert(r, uint256), convert(s, uint256)) == owner

in this case, the immutable PERMITTYPEHASH 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 PERMITTYPEHASH. in this case, since PERMITTYPEHASH 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.

Patches v0.3.10 (with 019a37ab98ff53f04fecfadf602b6cd5ac748f7f and #3586)

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?