Zcash plunges after four-year Orchard counterfeiting bug

An independent researcher disclosed on May 29, 2026 a four‑year vulnerability in Zcash’s Orchard shielded pool that could have allowed undetectable counterfeiting. Developers deployed an emergency fix and completed a network upgrade on June 3, 2026 to restore Orchard functionality.

The flaw was reported by researcher Taylor Hornby, who said the issue was found using Anthropic’s Claude Opus 4.8. The vulnerability affected Orchard, the component that manages shielded transactions. Technical details indicate an attacker could have created ZEC inside the shielded pool without leaving cryptographic evidence on the public ledger.

The Zcash Foundation coordinated a confidential response with protocol developers, miners, exchanges and other ecosystem participants before rolling out a corrected cryptographic circuit. The foundation reported no evidence the flaw had been exploited and stated that the overall ZEC supply remained intact after the upgrade.

Market data showed ZEC fell about 38%, from roughly $635 to an intraday low near $309, before recovering to about $330 in the days after the patch. The public disclosure reduced Zcash’s market capitalization and prompted concerns because shielded transactions do not produce a public trail that would prove whether counterfeit coins were created prior to the fix.

Hornby reported using an advanced language model to find the bug. Security researchers noted that more capable AI tools can accelerate the discovery of software flaws and can speed both offensive and defensive security work.

Zcash founder Zooko Wilcox proposed an upgrade called Ironwood to add features that would let users independently verify the cryptocurrency’s circulating supply. Developers and community members have called for additional audits and greater transparency around shielded-pool security.

Zcash launched in October 2016 by the Electric Coin Company and uses zk‑SNARK zero‑knowledge proofs to let users choose between transparent addresses and shielded ones. The network runs proof‑of‑work on the Equihash algorithm, has a 21‑million coin cap and distributes 80% of block rewards to miners and 20% to development funds governed by community decisions.

The project relied on a multi‑party “trusted setup” at launch; former ECC CEO Josh Swihart described Edward Snowden’s participation in that ceremony as: ‘He did it as a service, as a public good, and believing in privacy.’ Major upgrades included Sapling in 2018, which improved shielded transaction performance, and Orchard in May 2022, which added a unified address format and lighter mobile shielding.

Regulatory pressure and exchange decisions have affected privacy coins and Zcash listings over the years. In January 2026 the Zcash Foundation said the U.S. Securities and Exchange Commission closed its long‑running inquiry without recommending enforcement action. That month the Electric Coin Company’s staff reported they had been constructively discharged after a dispute with nonprofit board members. Independent development groups and external backers have continued protocol work and funding.

Community governance, upcoming protocol funding decisions and a scheduled halving in November 2028 remain on Zcash’s timeline. Developers are also transitioning node and wallet software, including a move from the C++ node to a Rust implementation and work on new wallets.