The delay is caused by a security issue found in one of the improvement proposals. A new schedule for the fork will be determined in an Ethereum dev call this Friday
Platform developers opted to move the fork. ChainSecurity AG, a Switzerland-based smart contract auditor, identified the vulnerability in Ethereum Improvement Proposal, or EIP, 1283 where attackers can take advantage to pilfer user funds.
The security issue which permits the same action to be done a number of times is labeled as Reentrancy Attack. Joanes Espanol of Amberdata told CoinDesk the attack enables the perpetrator to withdraw funds indefinitely. The attack is akin to the 2016 DAO attack.
ChainSecurity writes the usual gas needed to execute a contract is 2,300. The gas amount for ‘dirty’ storage operations would cost 200 gas versus the 5,000 gas cost of the network’s storage operations. Thus,
November last year was the initial prospected time for the Ethereum Constantinople fork. But, due to problems that arose from initiating the upgrade on Ropsten testnet, the fork was postponed.