Ironwood will retire Zcash’s old Orchard pool, route withdrawals through a turnstile and create a corrected shielded pool as the network addresses lingering uncertainty over possible hidden excess supply.
Zcash plans to use its July 28, 2026 Ironwood hard fork to contain any potentially forged ZEC tied to a past vulnerability in the Orchard shielded pool, as Zcash founder Zooko Wilcox outlined how the upgrade will handle uncertainty that cannot be fully resolved because Orchard hides transaction details. Ironwood, also known as NU6.3, is scheduled to activate at block 3,428,143 and will retire the current Orchard pool, introduce a new shielded pool with corrected cryptography and prevent users from sending or receiving ZEC inside the old pool after activation. Funds in the old pool will be able to leave only through a turnstile mechanism designed to ensure no more ZEC exits than legitimately entered, trapping any hypothetical excess value inside Orchard rather than letting it circulate more broadly. The flaw was discovered on May 29 by security researcher Taylor Hornby, and developers previously disabled Orchard activity before restoring it through the NU6.2 hard fork with corrected cryptography. Zcash said the bug was unlikely to have been exploited, but past abuse cannot be ruled out with complete certainty. Wallets, exchanges and other providers may temporarily pause services around the upgrade, and some users may need updated wallet support later to move funds into the new pool.