The Zcash network has upgraded to Ironwood: how the update closes a critical gap in private transactions
On July 28, at block #3,428,143 on the Zcash mainnet, the Ironwood upgrade was activated. This is not a scheduled update — it is a direct response to a critical vulnerability discovered in late May in the Orchard private transaction pool. Ironwood launches a new pool that will completely replace its compromised predecessor.
The issue was identified by Shielded Labs security engineer Taylor Hornby. While analyzing the code using Anthropic's AI model Opus 4.8, he discovered that the vulnerability had existed since the launch of Orchard in May 2022. Theoretically, it allowed the silent minting of fake ZEC. In the testnet, the researcher successfully generated counterfeit coins using a working attack code.
Developers patched the flaw in two stages in early June: first with a soft fork temporarily disabling Orchard transactions, then with a hard fork to restore network functionality. However, the key problem remained: the design of the private pool makes it cryptographically impossible to prove whether the vulnerability was actually exploited. Transaction amounts are hidden by design, and it is impossible to determine from the transactions themselves whether fake coins were created. Ironwood resolves this dilemma.
How Ironwood closes the issue
The update introduces a check at the pool boundary. Orchard has been placed in a restricted mode: new funds can no longer be deposited into it, and coins already placed are locked for internal transfers. Withdrawals are only possible through a "turnstile" into Ironwood. A mechanism is built into the protocol level to ensure that no more ZEC is withdrawn from the old vault than was deposited into it. As funds migrate, this will allow verification of the integrity of the supply without access to private transaction data. Ironwood operates on the corrected Orchard protocol, has undergone formal verification, and passed a third-party security audit.
What users need to do
The transition is implemented at the wallet level: applications supporting Ironwood will prompt users to move funds from the old vault. Creating a new wallet or changing addresses is not required — incoming transfers to existing Orchard addresses are automatically redirected to the new pool. In Zodl, migration is already available in manual mode, with an automatic option promised later. Users without assets in Orchard simply need to update their application.
The upgrade launch did not significantly affect the ZEC price. The date was known in advance — developers announced it on June 9. Over the past 24 hours, the coin has decreased by 4.3% to $468. As a reminder, after the vulnerability disclosure in early June, the ZEC price crashed by 48% to $302.48.
Expert opinion: Ironwood is not just a patch but a fundamental improvement to Zcash's privacy architecture. However, the most alarming signal for the community is the inability to cryptographically confirm that the vulnerability was not exploited by attackers over two years. This calls into question trust in the "trusted privacy" model that Zcash promotes as its core value.