Zcash Orchard Pool Counterfeiting Vulnerability
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anchored·5NL6tA…4H7eSummary
A critical soundness vulnerability in Zcash's Orchard shielded pool was discovered on May 29, 2026 by security engineer Taylor Hornby using Anthropic's Opus 4.8 AI model. The flaw, present since the Orchard pool's activation in May 2022, could have allowed a malicious prover to generate unlimited counterfeit ZEC undetectably within the shielded pool. An emergency soft fork and subsequent NU6.2 hard fork patched the vulnerability by June 3, 2026, prior to public disclosure on June 5, 2026, after which ZEC declined approximately 38% in 24 hours.
Connected Entities
3 entities · 28 linked investigations- Zcash Orchard Pool Counterfeiting Vulnerability→mentioned with→Zcash(70%)
- Zcash Orchard Pool Counterfeiting Vulnerability→mentioned with→BitMEX(70%)
Connected Through
2 shared actors · 28 investigationsDistinct actors this investigation shares with others — holders, traders, and named parties. Shared infrastructure (exchanges, pools) is excluded.
- □BitMEXorganizationalso inBitMart Exchange — Insolvency Claims and Frozen Withdrawals (August 2026)·0Holoworld AI — AVA Token Insider Bundling Scheme·0YZY Money·4JELLY·5H1 2026 Crypto Project Shutdown Wave (100+ Projects)·7BitMart Exchange Shutdown 2026·9BitMEX (2026 Class Action — Insider Trading and Liquidation Fraud)·10Arthur Hayes — Maelstrom CIO Exit Liquidity Allegations·14Harvest Finance·22Storj Labs·23BitMEX Exchange·28Zcash Orchard Pool Counterfeiting Vulnerability 2026·28Zcash Orchard Counterfeit Vulnerability·28BitMEX Closure (September 2026)·28BitMEX Exchange Closure September 2026·28Arthur Hayes (Maelstrom)·30MustStopMurad·38BitMEX Shutdown (September 2026)·38Rain·38CoinEx Exchange Closure (September 2026)·42Blockstream·42Avalanche·52Bitcoin Cash·54Ethena·55BitMEX·56Zcash Orchard Pool Counterfeiting Bug·62
- □Zcashorganization
Timeline(10 events)
May 2022
Orchard shielded pool activated via Zcash NU5 network upgrade; vulnerability introduced in halo2_gadgets scalar multiplication gadget.
Zcash Foundation / CoinDeskApril 2026
Shielded Labs engages Taylor Hornby as a security engineer to conduct proactive protocol vulnerability research.
CoinDesk29 May 2026
Taylor Hornby discovers the Orchard circuit soundness vulnerability using Anthropic's Opus 4.8 model and a custom AI auditing harness. Hornby constructs a working exploit generating unlimited counterfeit ZEC in a local regtest environment. Responsible disclosure made to ZODL core engineers the same evening.
The Block / CoinDesk31 May 2026
Private coordination with miners, exchanges, and node operators begins in preparation for emergency network response.
Zcash Foundation2 June 2026
Emergency soft fork activates at Mainnet block height 3,363,426 (approximately 02:00 UTC) via Zebra 4.5.3, disabling all Orchard-containing transactions and blocks.
Zcash Foundation3 June 2026
NU6.2 hard fork activates at Mainnet block height 3,364,600 (00:05 EDT) via Zebra 5.0.0, re-enabling Orchard with corrected circuit logic and a new consensus rule rejecting non-canonical proof sizes.
Zcash Foundation5 June 2026
Public disclosure of the vulnerability by Shielded Labs. ZEC declines approximately 37.8-38% in 24 hours, falling from approximately $635 to a low of approximately $309.
The Block / CoinDesk / Decrypt5 June 2026
Arthur Hayes, BitMEX co-founder, publicly discloses he has liquidated his entire ZEC position, citing the irresolvable uncertainty about whether counterfeiting occurred prior to the fix.
CoinDesk5 June 2026
Shielded Labs proposes a new network upgrade to create a fresh shielded pool with turnstile accounting on all existing Orchard coins to provide provable supply integrity.
The DefiantDecision Log
- hash: HJTR8KUGJwDtsBZPZEUS1XgBLmxBtrEFyfqphQvWeGNw
- hash: Cq3DA3xFKZvNxi7aNxNRKN3vrS6VncANVRBBPuDxQvc7
- hash: CEQifRMAqaDbTtEsCwPP4VPEDZpZkzDDwXQWrMVuYHDR
This investigation is cryptographically anchored to the Solana blockchain (3 events). 18 of 19 cited source URLs have an Internet Archive snapshot.
model: claude-sonnet-4-6
generated: 6/30/2026, 12:15:04 PM
last updated: 8/27/2026, 8:08:52 AM
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