According to Zcash Foundation, Zebra 4.4.0 was released recently to fix multiple consensus-level security vulnerabilities. The update addresses denial-of-service flaws that could halt block discovery, block signature operation (sigops) counting errors causing consensus disagreements, transparent transaction signature hash handling anomalies, and memory allocation amplification attack risks. The foundation strongly recommends all node operators upgrade immediately.
Some vulnerabilities could cause Zebra nodes to accept blocks rejected by zcashd, potentially triggering chain forks. Without timely updates, nodes risk block discovery interruption, consensus divergence, and resource exhaustion amplification. The foundation noted no alternative mitigation measures currently exist.