Vulnerability CVE-2021-39193

Frontier is Substrate's Ethereum compatibility layer. Prior to commit number 0b962f218f0cdd796dadfe26c3f09e68f7861b26, a bug in `pallet-ethereum` can cause invalid transactions to be included in the Ethereum block state in `pallet-ethereum` due to not validating the input data size. Any invalid transactions included this way have no possibility to alter the internal Ethereum or Substrate state. The transaction will appear to have be included, but is of no effect as it is rejected by the EVM engine. The impact is further limited by Substrate extrinsic size constraints. A patch is available in commit number 0b962f218f0cdd796dadfe26c3f09e68f7861b26. There are no workarounds aside from applying the patch.