Zcash Emergency Upgrade Fixes Critical Bug as ZEC Eyes $610 Breakout

Zcash Foundation patches a critical Orchard circuit bug via emergency hard fork as ZEC trades above $610 resistance. Here’s what happened.

The Zcash Foundation moved fast last week. A critical soundness vulnerability discovered in the Orchard Action circuit triggered a two-stage emergency protocol upgrade. 

The Foundation released Zebra 4.5.3 followed by Zebra 5.0.0 to contain and fix the flaw. 

According to the Foundation, no exploitation occurred, and the total ZEC supply remained intact throughout. Meanwhile, ZEC is trading around $619 as traders watch a key technical resistance level closely.

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Zcash Foundation Releases Emergency Zebra Upgrade to Patch Orchard Bug

The vulnerability was first uncovered on May 29 by Taylor Hornby, an independent security researcher running an ongoing protocol audit for Shielded Labs. Hornby responsibly disclosed the issue to ZODL core engineers that same evening.

Engineers Daira-Emma Hopwood, Kris Nuttycombe, and Jack Grigg confirmed the bug within hours. Work on a fix began immediately. The team kept details of the flaw private during that period to reduce exploitation risk before a patch could go live.

The Zcash Foundation describes the bug as a soundness vulnerability in the halo2_gadgets crate. In simple terms, a soundness flaw means the system could accept transactions it should reject. 

The Foundation noted that successful exploitation could have allowed double-spending within the Orchard pool, though it could not inflate the total ZEC supply due to Zcash’s turnstile mechanism.

Private coordination with miners and exchanges began on the evening of May 31. 

A first soft-fork activation attempt faced deployment challenges, but a second patch targeting block height 3,363,426 activated successfully at around 02:00 UTC on June 2.

How the Two-Stage Hard Fork Worked and What Changed

Zebra 4.5.3 served as the first line of response. It implemented an emergency soft fork that temporarily disabled all Orchard actions at mainnet block height 3,363,426. 

Under this version, nodes rejected any transaction or block containing Orchard actions after that height. The Foundation noted that 4.5.3 did not penalize peers still relaying Orchard-containing data, preserving network connectivity during the transition window.

Disabling Orchard first was a deliberate decision. 

The Foundation explained that releasing a direct patch too early would have exposed details of the vulnerability to anyone who could read the updated code. Disabling it first bought time to finalize the circuit fix without tipping off potential bad actors.

Zebra 5.0.0 then activated the NU6.2 hard fork at mainnet block height 3,364,600 on June 3. This version re-enabled Orchard using a corrected circuit and permanently closed the vulnerability. 

The Foundation clarified that a hard fork was necessary because fixing a zero-knowledge proof circuit requires updating the pinned verifying key, something a simple node software patch cannot do alone.

The Foundation confirmed the Orchard pool’s total supply remained intact throughout, verified by Zcash’s turnstile mechanism. 

Sapling and transparent transactions were unaffected at all times. All Zebra node operators are now strongly urged to upgrade to version 5.0.0.

ZEC Price Approaches $610 Resistance as Market Watches Closely

On the price side, ZEC is drawing attention from technical analysts. 

Crypto trader Ardi flagged the $610 level as a critical zone on social media, describing it as a multi-timeframe resistance pivot. According to Ardi, multiple pushes toward $650 have been sold back below $610, pointing to trapped liquidity sitting above that region.

Ardi noted that if ZEC continues to reject at $610, the market may be forming a macro lower high before moving lower. 

On the other hand, a reclaim of $610 with multiple sustained closes above it could push price toward local highs just below $700. The trader added that the cleanest risk/reward for buyers remains at a confirmed break of range highs, not before.

Per CoinGecko data, ZEC trades at $619.47 with a 24-hour trading volume of over $1.4 billion. The token is up 8.50% in the past 24 hours and 7.51% over the past seven days.

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