Zcash executed an emergency protocol-level change on the night of June 1, 2026, after developers caught a vulnerability inside the Orchard shielded pool. The fix activated at mainnet block height 3,363,426, roughly 02:00 UTC on June 2. Miners across the network were asked to stop processing Orchard transactions while the coordinated upgrade rolled out.

The Zcash Open Development Lab, known as ZODL, confirmed the issue in a public statement. The flaw was spotted during weekend security reviews before any known exploitation occurred. All funds and user privacy, the lab said, were unaffected.

Orchard Only. The Rest Keeps Running

The suspension hit only Orchard, Zcash’s newest shielded pool. Sapling shielded transactions and transparent pool activity continued without interruption. ZEC held on exchanges was also unaffected, meaning trading carried on normally through the upgrade window.

ZODL posted on X that the protocol-level change had taken effect at 22:30 EDT on June 1. Wallet users sending or receiving Orchard funds were cut off until the rollout finished. The lab initially told the community to expect Orchard transactions back online by 14:00 EDT on June 2.

That window slipped. Mining pools asked for more time.

Miners Asked for More Time Across Time Zones

In a follow-up post on X, ZODL said several mining pools needed extra runway to finish deployment and quality-control checks. The coordination challenge, it said, involved teams spread across multiple time zones. The revised target moved to approximately 23:00 EDT on June 2.

The upgrade itself covered both consensus node implementations running on the Zcash network, zcashd and zebrad, along with SDKs and other supporting infrastructure. That dual-node coordination is something most privacy coin networks do not deal with. Running two separate client implementations adds redundancy but also means upgrade rollouts require double the confirmation before the network can move forward cleanly.

ZODL was direct in its second update.

“There is no evidence of any exploit. Your funds and privacy are safe. No user action is needed.”

A Monero parody account, @monerify, on X pushed back publicly asking what type of exploit was actually found. ZODL replied again, repeating that no exploit had been confirmed.

Cake Wallet Users Felt It First

Seth For Privacy, a privacy advocate and developer, posted on X that Zcash functionality inside Cake Wallet would not work during the outage. His note was direct.

“No details yet, but a major issue has led to the Zcash network doing a rapid fork, and includes miners temporarily refusing to mine Orchard transactions. This means that Zcash in Cake won’t work ATM due to the broader network issues, and unfortunately there isn’t anything we can do about that as it’s a network-wide issue.”

Cake Wallet routes ZEC transactions through Orchard by default, meaning the entire ZEC feature set inside the wallet went offline. For users who rely on Cake specifically because it defaults to shielded transactions, the outage was not a minor inconvenience. Privacy-first wallets with Orchard as the default are precisely the tools that matter most to users in regions where financial surveillance is a real concern, not a theoretical one.

Seth For Privacy added he would update when the situation changed.

What the GitHub Release Actually Said

The official zcash/zcash v6.12.5 release on GitHub described the fix as addressing multiple consensus and denial-of-service vulnerabilities in zcashd. The release notes said those vulnerabilities were reachable by a remote peer or miner. Mining nodes that had not upgraded before activation were warned they could produce blocks the upgraded majority would reject, leading to high orphan rates.

That is a harder disclosure than ZODL’s public communications suggested. Exchanges and operators were told to upgrade within the same window to stay in consensus. A second release, covering Orchard’s re-enablement, was also flagged as required shortly after the soft fork activated.

The Zcash Community Forum post from ZODL described the effort as relying on voluntary cooperation among independent participants. The lab also said it was notifying maintainers of other protocols that have deployed Orchard as part of responsible disclosure.

ZODL said additional information would be shared after the upgrade completed.