Zcash Jumps More Than 10% After Emergency Zebra Update Fixes Orchard Flaw

Zcash (ZEC) climbed more than 10% after the Zcash Foundation rolled out emergency upgrades for Zebra, its node software, to address a critical bug in Orchard and restore full network functionality. Developers said they identified a soundness vulnerability in Orchard's zero-knowledge proof circuit, triggering a rapid security response across the ecosystem. The Foundation released Zebra 4.5.3 and Zebra 5.0.0 to resolve the issue. Zebra 4.5.3 implemented an emergency soft fork that temporarily disabled Orchard actions. Zebra 5.0.0 activated NU6.2 and reenabled Orchard with a corrected circuit. Market Reaction as Orchard Returns ZEC drew strong attention after the Foundation confirmed the fix was live, rising more than 10% even as the broader crypto market stayed under pressure. The move reflected renewed confidence after the Orchard pool was brought back online. The Foundation urged node operators to upgrade to Zebra 5.0.0 as soon as possible. Operators unable to move to 5.0.0 before the NU6.2 activation height were advised to use Zebra 4.5.3 to stay on the correct chain during the upgrade window. Separately, growing interest in digital privacy is increasingly being cited alongside Zcash's recent price action. Will McEvoy shared a chart comparing Google Trends data for "privacy" with ZEC on a logarithmic scale, showing both rising sharply into 2026. The data indicates privacy-related attention has reached its highest level in the chart period, while ZEC has moved toward the top end of its recent range. How the Orchard Vulnerability Was Found The flaw was discovered on Friday, May 29, by independent security researcher Taylor Hornby during a protocol audit supported by Shielded Labs. Hornby disclosed the issue to ZODL core engineers, who confirmed it within hours and began preparing a fix. The bug impacted the Orchard zero-knowledge proof circuit implementation in the halo2_gadgets crate. A soundness bug can cause a system to accept an invalid transaction or state transition; in this case, it could have enabled double-spending within Orchard. Zcash's turnstile mechanism, however, protected the total ZEC supply. Emergency Soft Fork and NU6.2 Activation Private coordination with miners and exchanges started on Sunday, May 31. After an initial activation attempt ran into deployment issues, engineers released another patch targeting block height 3,363,426. The soft fork went live at about 02:00 UTC on June 2. Under Zebra 4.5.3, blocks and transactions containing Orchard actions were temporarily rejected. Sapling and transparent transactions continued to function during the incident. NU6.2 activated on Wednesday, June 3, at 00:05 EDT. The hard fork reenabled Orchard actions using the corrected circuit and updated the required verifying key. The Foundation said a hard fork was necessary because the proof circuit change could not be handled through a standard software patch. Zebra 5.0.0 activates NU6.2 at Mainnet block height 3,364,600 and Testnet block height 4,052,000. It also introduces consensus rules rejecting Orchard bundles with noncanonical proof sizes from the activation height, closing the vulnerability that the earlier soft fork mitigated. No Signs of Exploitation or Value Creation The Zcash Foundation said the vulnerability was fixed before any known exploitation occurred and added there was no evidence of unauthorized value creation. The turnstile mechanism confirmed total supply integrity throughout the incident, and user privacy was not impacted. The Foundation credited Taylor Hornby, Shielded Labs, ZODL engineers, Zebra contributors, miners, node operators, exchanges, wallet providers, and infrastructure teams for supporting the coordinated upgrade that restored Orchard operations.