Summary
- Zcash experienced a significant decline after a four-year-old flaw in its Orchard shielded pool was revealed.
- This vulnerability, identified through AI-enhanced auditing, could have enabled the creation of unlimited counterfeit ZEC without detection.
- Critics suggest that privacy coins present a unique set of risks where such vulnerabilities may go unnoticed.
Zcash saw a sharp decline following the announcement of a severe vulnerability in its Orchard shielded pool, which had the potential to facilitate undetectable counterfeiting for more than four years.
According to CoinGecko data, the privacy coin fell from a high of $635 on Wednesday to a low of $309 on Thursday, before slightly recovering to around $330, marking a decrease of 37.8% for the day.
— zooko🛡🦓🦓🦓 ⓩ (@zooko) June 4, 2026
This flaw was uncovered on May 29 by security expert Taylor Hornby using AI-assisted tools for auditing.
It was rooted in two lines of code within the Orchard circuit, which handles Zcash's shielded transactions, allowing a malicious party to generate counterfeit ZEC in the shielded pool without any on-chain signature. If this vulnerability had been exploited prior to its discovery, it would have been impossible to prove any wrongdoing.
According to Shielded Labs, the organization responsible for Zcash's development, "The vulnerability existed from the time of Orchard's activation in May 2022 until an urgent fix was applied on June 1, 2026." They added, "Given the privacy characteristics of Orchard and the nature of the flaw, it is not possible to definitively ascertain, based solely on cryptography, whether exploitation has occurred."
This situation has reignited discussions about a fundamental issue that critics argue extends beyond this particular flaw. Unlike Bitcoin and Ethereum, which allow for immediate visibility of on-chain exploits, privacy coins like Zcash create circumstances where a successful attack could remain undetected.
Crypto analyst Udi Wertheimer commented, "Zcash enables a unique class of bugs where, if they're exploited, no one would know. This unique risk continues to exist. The fact that this specific bug was fixed is irrelevant."
Joe Andrews, CEO of Aztec Labs, a privacy-focused product studio, noted that the under-constrained elliptic curve checks, which are central to this vulnerability, are common flaws found in production ZK circuits. He stated that this pattern is not new to Zcash and that AI is expediting the identification of such issues across the sector.
Andrews proposed that a comprehensive solution would involve formal circuit verification alongside a secondary proof system, a strategy that Ethereum is already pursuing. He explained, "Both systems must concur for a state transition to be deemed valid, which significantly reduces the likelihood of bugs being exploited."
Market Reaction Mixed
Arthur Hayes, former BitMEX CEO, revealed that he sold off his entire Zcash holdings following the news.
The immediate concern for investors is not inflation across the network but the possible insolvency of the Orchard pool itself, which could lead to dilution of shielded ZEC holders if counterfeit claims compete with legitimate claims for a limited pool balance.
The Holy Trinity is dead. Sadly due to the Orchard Pool exploit, I had to dump our entire $ZEC bag.
- While I think it's extremely unlikely of any minting, it cannot be formally cryptographically proved impossible
- The privacy from AI, govt, big tech narrative demands perfection…— Arthur Hayes (@CryptoHayes) June 5, 2026
Conversely, not everyone is as alarmed. Craig Salm, Grayscale's chief legal officer, expressed skepticism about the likelihood of exploitation before the patch was implemented. He suggested that for someone to exploit the vulnerability, they would have needed to scrutinize the codebase more thoroughly than all core developers combined and then resist the temptation to drain the entire pool during a significant bull market. "Seems unlikely to me," he stated.
In response to the situation, Shielded Labs has proposed a network upgrade that would introduce a new shielded pool with turnstile accounting, allowing for verification of the Zcash supply's integrity.
Andrews mentioned that the design of this upgrade, which mandates all coins to unshield prior to entering the new pool, effectively limits the risk from any previous exploitation to the current amount of shielded assets. He asserted, "Formal verification of the new upgrade further minimizes risks significantly."