Zcash Completes Emergency Network Upgrade After Critical Privacy Pool Bug Discovery

Jun 3, 2026

Independent security researcher Taylor Hornby discovered a critical double-spending vulnerability in Zcash's Orchard shielded pool on May 29, 2026. Developers executed a two-stage fix: an emergency soft fork on June 2, 2026 halted Orchard activity at block 3,363,426, then the NU6.2 network upgrade on June 3, 2026 permanently restored functionality using a corrected cryptographic circuit. The Zcash Foundation urged node operators to upgrade to Zebra 5.0.0. No exploitation occurred.

Orchard privacy pool vulnerability

▪The total supply of ZEC was never at risk from the Orchard privacy pool vulnerability
▪The Zcash Orchard pool was introduced in 2022
▪A critical bug in Zcash's Orchard privacy pool was discovered on May 29, 2026 that could have enabled double-spending
▪No exploitation of the Zcash Orchard privacy pool bug occurred
▪Taylor Hornby disclosed the Zcash Orchard privacy pool flaw to Zcash Open Development Lab (ZODL) engineers on the evening of May 29, 2026
▪Independent security researcher Taylor Hornby discovered the Zcash Orchard privacy pool vulnerability on May 29, 2026

Emergency network upgrade process

▪The Zcash Foundation urged all node operators to upgrade immediately to Zebra 5.0.0
▪ZODL founder Josh Swihart described the Zcash emergency network upgrade as the most ambitious network upgrade in Zcash's history given the time available and the number of parties involved
▪A second Zcash emergency soft fork activation attempt succeeded early on June 2, 2026, halting all Orchard activity at block 3,363,426
▪The Zcash Foundation disclosed on June 3, 2026 that it quietly patched a critical flaw in the privacy cryptocurrency's core transaction system
▪The permanent Zcash fix arrived on June 3, 2026, when a full network upgrade dubbed NU6.2 restored Orchard functionality using a corrected circuit
▪Private coordination with Zcash miners and exchanges began on the evening of May 31, 2026

Block explorer confusion

▪The Zcash blockchain kept producing blocks the entire time during the upgrade, with miners continuing to operate and transactions continuing to confirm
▪The Zcash network was running as normal after the upgrade, but block explorers were temporarily impacted as they upgraded their own network nodes

ZEC price performance

▪ZEC's 30-day rise as of June 3, 2026 is above 53%
▪ZEC remains well off its all-time peak of $3,191 set in 2016
▪ZEC is up more than 50% over the 30 days preceding June 3, 2026
▪ZEC is up more than 10% over the 24 hours preceding June 3, 2026, at a recent price near $629
▪ZEC reached a recent high of nearly $700
▪ZEC is up 1,084% over the year preceding June 3, 2026