The Zcash blockchain has resumed normal block production following the emergency protocol upgrade that addressed a critical Orchard circuit bug. According to Zcash block explorers, block 3,364,601 was the last block created at 5:27 AM UTC, with the network experiencing a four-hour halt in block production on June 3, 2026. The NU6.2 hard fork activated at mainnet block height 3,364,600 on June 2, 2026, successfully re-enabling Orchard actions with a corrected circuit and routing Orchard proofs to a new per-circuit verifying key. This represents a complete recovery from the severe disruption that had brought 96 missed blocks and effectively frozen all transaction confirmations across the payment system.
The blockchain halt occurred just days after Zcash validators successfully implemented an emergency protocol upgrade on June 1, addressing a critical vulnerability in the Orchard shielded pool. As per the latest announcement, the Zebra 4.5.3 emergency soft fork activated at mainnet block height 3,363,426 on June 2, temporarily rejecting transactions and blocks containing Orchard actions while engineers prepared a corrected circuit. The NU6.2 hard fork then re-enabled Orchard actions with the new verifying key, marking the second security-driven protocol upgrade in Zcash history since 2016. The bug was discovered on May 29 by independent security researcher Taylor Hornby during a protocol audit for Shielded Labs, with ZODL engineers confirming the issue within hours and beginning work on a fix. The foundation emphasized that no unauthorized value appeared and that Zcash's turnstile mechanism protected total ZEC supply.
The emergency upgrade has temporarily suspended Orchard transactions while validators implemented the coordinated upgrade, with wallet users currently unable to send or receive Orchard funds until the rollout is complete. However, the rest of the Zcash network remained operational throughout the incident, with transactions involving the older Sapling shielded pool, transparent addresses, and exchange-held ZEC balances continuing to function normally. The recent blockchain halt had further compounded service disruptions, but user privacy was not harmed during the incident and Sapling and transparent transactions operated normally while Orchard actions remained paused. The foundation has assured users that no funds were lost and privacy remains intact throughout the upgrade period, with the affected code including older halo2_gadgets, orchard and zcash_primitives releases, plus zcashd versions 5.0.0 through 6.12.3.
ZEC dropped 2% in the hour following the four-hour mark of the halt, with selling pressure accelerating precisely as the duration made denial impossible for broader market participants. This mirrors the pattern seen across other network disruption events, with initial slow reaction followed by sharp declines once the duration becomes apparent. Despite the technical challenges, Zcash (ZEC) has surged 8% over the past week and gained 46% in the last month, according to CoinDesk data, demonstrating resilience against broader market weakness. The token had staged an extraordinary recovery from its July 2024 lows under $1, surging over 16x to the $250 range by April 2026, with a 16% single-day spike to $372 recorded on April 9, 2026, and another sharp 30% move in May that put the coin at above $600. However, the structural read remains bearish until block production resumes and an official explanation confirms the halt is contained.
The disclosure that Zcash is notifying maintainers of other protocols that have deployed Orchard suggests the issue may extend beyond Zcash's own implementation and could potentially affect projects that utilize Orchard-related technology. Developers have not yet released full technical details, a common practice during active security upgrades to reduce the risk of exploitation before fixes are broadly deployed. The NU6.2 hard fork required a new pinned verifying key, making it a mandatory upgrade for all node operators. The foundation has strongly urged all node operators to upgrade to Zebra 5.0.0 as soon as possible, with operators that stayed on incorrect forks after NU6.2 potentially needing to resync from scratch or restore from backups made before activation. The recent blockchain halt serves as a stark reminder that even well-established cryptocurrencies can experience significant technical disruptions despite robust security measures, though the swift response and successful resolution demonstrate the network's resilience.
