Zcash rallies 10% as privacy upgrade scare clears
In brief
- Zcash spiked 10% to $620 while Bitcoin and Ethereum dropped over 4%.
- Block explorers appeared stale after emergency upgrade, falsely suggesting blockchain halted.
- Developers disabled Orchard transactions via soft fork to patch soundness vulnerability.
- NU6.2 hard fork re-enabled Orchard with corrected circuit at block 3,364,600.
The scare that wasn't
Zcash did not go offline, but part of its privacy system was deliberately shut down to carry out the most ambitious network upgrade in Zcash's history. The confusion started after Zcash completed an emergency network upgrade to restore Orchard, the shielded pool that underpins the network's most advanced privacy transactions.
Some block explorers appeared to be stale after the upgrade, giving the impression that the blockchain had stopped. Infrastructure operators later said those explorers were catching up or resyncing after their nodes upgraded, while miners continued to produce blocks and transactions continued to be confirmed. The blockchain worked the whole time.
Why the emergency fix
Developers had temporarily disabled Orchard transactions through an emergency soft fork while they prepared a permanent fix for a soundness vulnerability in the Orchard zero-knowledge proof circuit. The Zcash Foundation said the vulnerability was discovered May 29 by independent security researcher Taylor Hornby, who was conducting protocol security research for Shielded Labs.
The response unfolded in two stages. The first stage was activated at block height 3,363,426 and rejected Orchard-containing transactions and blocks. The second stage came with the NU6.2 hard fork, which activated at block height 3,364,600 early Wednesday and re-enabled Orchard using a corrected circuit.
What Orchard is
Orchard is the network's newest shielded pool and was introduced with the NU5 upgrade in 2022. Unlike earlier Zcash privacy pools, Orchard uses Halo 2 and does not require a trusted setup. That distinction matters because prior pools relied on a trusted setup ceremony, a long-running concern in privacy-coin infrastructure.
The bug affected the soundness of the Orchard circuit, meaning a system should accept only valid transactions and valid state changes. Successful exploitation of the soundness flaw could have allowed double-spending inside Orchard. The issue did not allow an attacker to inflate Zcash's total supply.
Market context
The rally turned Zcash into a rare winner amid a broader crypto sell-off tied to renewed geopolitical stress, weaker digital-asset sentiment, and forced liquidations of leveraged positions. Most major assets retreated, but ZEC's 10% gain and the swift resolution of the upgrade scare highlighted the importance of transparent communication during network maintenance.
