The Zcash Foundation has released an emergency security update for its node client, Zebra, with version 4.5.0. This update addresses a critical consensus-level vulnerability and several high-severity denial-of-service (DoS) issues. Node operators are urged to upgrade immediately to prevent potential exploits. Key fixes in this release include resolving a sigop counting error in P2SH script parsing, a caching logic flaw in NU5 block validation, and a risk of crash due to transparent-address balance overflow. Additionally, the update addresses multiple vulnerabilities in RPC interfaces and mempool handling that could lead to node stalling, restart loops, or permanent shutdown.