Solana's legacy consensus mechanism contains a protocol-valid clock attack vulnerability that allows malicious leaders to manipulate transaction ordering and suppress honest block proposals.

"The paper describes a protocol-valid way for a scheduled leader to stretch its effective block window and suppress honest leaders' proposals in a fork-assisted version. The path relies on Proof-of-History and TowerBFT, the machinery Alpenglow is intended to replace but had not yet displaced on mainnet in Agave 4.2."