The long-awaited Ethereum Constantinople Hard Fork has been delayed due to security glitches.
The Constantinople Hard Fork is the second phase of the Metropolis project, it is supposed to be the most important and considerable one, aiming to increase ETH network’s performance and blockchain speed. The fork is supposed to be implemented after block number 7,080,000 is mined and has been scheduled between January 14th and 18th. It is embarked as a process of passing from Proof of work (PoW) protocol to Proof of Stake (PoS) protocol.
The Constantinople is considered a hard fork as the blockchain will split in two. It is also expected to reduce mining rewards from three to two. This Hard Fork is non-contentious and all transaction validators must upgrade their software.
Although the Constantinople Hard Fork is considered a positive upgrade, the Ethereum Core Developers and the Ethereum Security Community have been informed for potential issues, as identified on January, 15th 2019. These disturbing news have led to the long-awaited Ethereum Constantinople Hard Fork to be postponed out of security considerations.
The upgrade creates cheaper gas cost for certain SSTORE operations. As an unintended side effect this enables re-entrancy attacks when using address.transfer(…) or address.send(…) in Solidity smart contracts. At an earlier stage these functions were not considered vulnerable, however now it appears that they may lead to re-entrance attacks.
The eventual vulnerabilities are being currently investigated and so far no new hard fork date has been announced.