Zcash network operators can now sync blockchain data up to five times faster using the newly deployed Zakura node, as the ecosystem prepares for the Ironwood hard fork slated for July 28, 2026. The upgrade will address a critical bug found in the existing shielded pool.
Details on Ironwood Hard Fork and Bug Fix
The Ironwood update, also known as NU6.3, activates at block 3,428,143, approximately on July 28 at 8 a.m. EST. It disables the old Orchard shielded pool due to a soundness flaw discovered in its cryptographic circuits. This flaw could theoretically allow creation of counterfeit ZEC without detection because of the privacy features that restrict external verification. After the bug was identified in late May 2026 by security researcher Taylor Hornby from Shielded Labs, developers implemented a temporary soft fork and a patch (NU6.2) to prevent exploitation.
Once Ironwood is live, the old shielded pool will no longer accept new deposits or internal transfers. Users will still be able to move existing coins through a newly introduced checkpoint known as the turnstile, which prevents outflows exceeding inflows, thereby guaranteeing the verifiability of total ZEC supply without requiring every user to migrate coins immediately. In case counterfeit coins exist, the turnstile will block excess outflows and destroy such coins, providing transparent proof of any prior exploitation.
Formal verification of the new Ironwood cryptographic circuits is underway via Project Tachyon to supplement manual code reviews with machine-checked proofs. Node operators must upgrade before the fork block height to avoid service interruptions. Wallets affiliated with the Zcash Open Development Lab will assist users in migrating shielded funds, although those holding only transparent or non-Orchard balances are not required to act. The legacy zcashd node software is also scheduled to be deprecated around the same time.
Sean Bowe and Dev Ojha’s Zakura node already demonstrates syncing speeds five times faster than the widely used Zebra node, facilitating quicker network participation and validation for node operators ahead of the upgrade.
ZEC’s price took an initial hit following the May bug disclosure but has remained stable above $500 since then.
material is informational and not financial advice
