CVE-2026-46540 Nimiq light-blockchain: Light blockchain rebranch issue

Nimiq is a Rust implementation of the Nimiq Proof-of-Stake protocol based on the Albatross consensus algorithm. Prior to version 1.4.0, when LightBlockchain::rebranch adopts a fork chain whose tip is a macro block checkpoint or election, it only updates self.head but fails to update self.macrohea...