Vulnerabilities > CVE-2021-41153 - Always-Incorrect Control Flow Implementation vulnerability in EVM Project EVM
Summary
The evm crate is a pure Rust implementation of Ethereum Virtual Machine. In `evm` crate `< 0.31.0`, `JUMPI` opcode's condition is checked after the destination validity check. However, according to Geth and OpenEthereum, the condition check should happen before the destination validity check. This is a **high** severity security advisory if you use `evm` crate for Ethereum mainnet. In this case, you should update your library dependency immediately to on or after `0.31.0`. This is a **low** severity security advisory if you use `evm` crate in Frontier or in a standalone blockchain, because there's no security exploit possible with this advisory. It is **not** recommended to update to on or after `0.31.0` until all the normal chain upgrade preparations have been done. If you use Frontier or other `pallet-evm` based Substrate blockchain, please ensure to update your `spec_version` before updating this. For other blockchains, please make sure to follow a hard-fork process before you update this.