Zcash Orchard Pool Counterfeiting Vulnerability 2026
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anchored·3Sxz8n…A5L2Summary
On June 5, 2026, Shielded Labs publicly disclosed a critical soundness flaw in the zero-knowledge proof circuit of Zcash's Orchard shielded pool that had existed undetected since the pool's activation in May 2022. The vulnerability, found by security engineer Taylor Hornby using Anthropic's Claude Opus 4.8 AI model, could have allowed unlimited undetectable counterfeit ZEC minting with no on-chain signature; an emergency hard fork patched the circuit by June 3, 2026. Because Orchard's privacy design conceals transaction history, no cryptographic method exists to determine whether the flaw was exploited during the four years it was present, leaving the supply integrity of shielded ZEC permanently unverifiable for that period.
Connected Entities
2 entities · 26 linked investigations- Zcash Orchard Pool Counterfeiting Vulnerability 2026→mentioned with→BitMEX(65%)
Connected Through
1 shared actor · 26 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 Counterfeit Vulnerability·28BitMEX Closure (September 2026)·28BitMEX Exchange Closure September 2026·28Arthur Hayes (Maelstrom)·30MustStopMurad·38BitMEX Shutdown (September 2026)·38Rain·38Zcash Orchard Pool Counterfeiting Vulnerability·40CoinEx Exchange Closure (September 2026)·42Blockstream·42Avalanche·52Bitcoin Cash·54Ethena·55BitMEX·56Zcash Orchard Pool Counterfeiting Bug·62
Timeline(10 events)
May 2022
Zcash Orchard shielded pool activated on mainnet, beginning the period during which the counterfeiting vulnerability was present and undetected.
CoinDeskApril 2026
Shielded Labs engages Taylor Hornby as an independent security engineer to conduct a targeted protocol security audit of Zcash.
Unchained Crypto29 May 2026
Taylor Hornby discovers the soundness flaw in the Orchard zero-knowledge proof circuit using Claude Opus 4.8 in an AI-assisted audit. He discloses the vulnerability to Zcash Open Development Lab (ZODL) and creates a working exploit in a local test environment.
CoinDeskJune 2026
Emergency soft fork coordination begins; Zebra 4.5.3 release prepared to disable Orchard transactions at a specific block height.
CryptoTimes2 June 2026
Emergency soft fork activates at mainnet block height 3,363,426 at approximately 02:00 UTC, temporarily disabling all Orchard transactions. A 25-block fork and 37 orphaned blocks result from nodes running outdated software.
CryptoTimes3 June 2026
NU6.2 hard fork activates at block height 3,364,600 via Zebra 5.0.0, re-enabling the Orchard pool with a corrected circuit that introduces a copy_advice() equality constraint. ZEC briefly rallies from approximately $544 to $624.
CoinTelegraph4 June 2026
ZEC reaches a local high of approximately $624 in the aftermath of the confirmed patch. Arthur Hayes holds ZEC as his second-largest fund position at this point.
BitMEX Blog5 June 2026
Shielded Labs publishes the public disclosure of the Orchard counterfeiting vulnerability, authored by Jason McGee. ZEC crashes approximately 38-50% within 24-48 hours, falling to a low of $309. Arthur Hayes publicly announces he has liquidated his entire Zcash position, citing that the exploit's occurrence cannot be cryptographically ruled out.
CoinDesk15 June 2026
Shielded Labs updates the original disclosure post, per page metadata on the official article.
Shielded LabsDecision Log
- hash: GRzr9W9uEaVVo2fKGJF66ypgUp4YV3DxG6GtwzCmTgPC
This investigation is cryptographically anchored to the Solana blockchain (1 event). 15 of 15 cited source URLs have an Internet Archive snapshot.
model: claude-code-investigator
generated: 6/29/2026, 12:18:51 PM
last updated: 7/27/2026, 6:38:44 AM
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