# Aztec relaunches zk.money on a network whose proving system still has an unfixed critical flaw

Every private transfer is capped below $2,500 and co-signed by a separate protocol's sealed servers while the circuit fix waits for the V6 release.

- Published: 2026-09-30T06:00:33.939Z
- Canonical: https://polylog.news/crypto/2026-09-30/aztec-relaunches-zk-money-on-a-network-whose-proving-system
- Publisher: Polylog (Crypto desk)
- Section: crypto
- Sources: [CoinDesk](https://www.coindesk.com/tech/2026/09/29/embargo-12-et-ethereum-users-get-another-way-to-pay-privately-as-zk-money-returns-after-three-years), [Aztec Network (disclosure)](https://aztec.network/blog/alpha-v5-proving-system-vulnerability), [Aztec Network (Alpha V5)](https://aztec.network/alpha-v5), [The Block](https://www.theblock.co/news/defi/2026-09-29-aztec-zk-money-privacy-wallet-ethereum-layer-2-417174)

Aztec Labs brought back zk.money on Monday, three years after shutting it down, as a self-custodial wallet for private stablecoin payments on the Aztec layer-2 network. Transfers between users hide amounts and counterparties from the public chain, while deposits arriving from Ethereum stay visible, [CoinDesk reported](https://www.coindesk.com/tech/2026/09/29/embargo-12-et-ethereum-users-get-another-way-to-pay-privately-as-zk-money-returns-after-three-years). Each transfer must stay below $2,500, and a separate protocol called Oxide runs sealed servers that co-sign every send and withdrawal, [according to The Block](https://www.theblock.co/news/defi/2026-09-29-aztec-zk-money-privacy-wallet-ethereum-layer-2-417174).

Those limits exist because the underlying network is running with a known defect. Aztec core contributors [disclosed a critical vulnerability](https://aztec.network/blog/alpha-v5-proving-system-vulnerability) in the [Alpha V5](https://aztec.network/alpha-v5) proving system, found through internal artificial-intelligence-assisted auditing. An attacker could potentially construct a proof that passes verification for a transaction the network should reject, allowing the chain to accept a state transition outside the rules Alpha V5 is supposed to enforce. Contributors also state that they cannot determine from chain history whether anyone used the flawed path, because the system does not record enough information to distinguish ordinary accepted transactions from transactions accepted through the flaw. The fix is deferred to the V6 release, which is meant to include circuit updates that reject proofs tied to the affected system.

This is the failure mode that ordinary rollup safety mechanisms do not catch. Optimistic rollups rely on re-execution and fraud proofs. Validity rollups rely on the soundness of the circuit itself. When the circuit is unsound, that guarantee no longer holds, so the operator must substitute administrative controls, including value caps, application-level guards, and a co-signing service. Aztec is a testnet-stage alpha network and says so, but the design of zk.money shows what that trade-off means in practice. A user gets cryptographic privacy from the public, and for now, a non-cryptographic dependency on an external signer for both liveness and safety.

For context on scale, the layer-2 sector Aztec is entering secures $51.09 billion in total value according to L2Beat, with Base Chain at $16.19 billion and the largest zero-knowledge network in that set, Starknet, at $455.7 million. Aztec is betting that networks need confidential execution more than additional throughput. This disclosure shows what that bet costs while the proving stack is still being built.

## What this means

The mechanism is trust substitution. When a validity proof stops bounding state transitions, the guarantee shifts from mathematics to whoever operates the manual controls, in this case Aztec's transfer caps and Oxide's sealed co-signing servers. Users of zk.money, application teams building on Alpha V5, and any bridge exposed to Alpha V5 state carry that risk directly. Aztec faced a similar problem before, with the Alpha V4 vulnerability that forced users to withdraw ahead of a deadline in June, and the same pattern repeated at the next version. The likelier outcome over the coming months is that privacy and zero-knowledge networks ship with explicitly disclosed non-cryptographic backstops, caps, and manual override mechanisms as standard practice, and that competitors advertise proof-system diversity as a feature. What would prove that read wrong is a V6 release with independently reviewed circuit changes that lets Aztec remove both the value cap and the external co-signer without an incident.

## What to watch

- Whether V6 ships with circuit changes that reject proofs from the affected system, and whether network operators are required to upgrade rather than asked to.
- Whether the $2,500 transfer cap on zk.money is raised or removed, which would indicate the team considers the proving path fixed.
- Whether Oxide's co-signing servers get an independent public review, since they are currently a single dependency for both privacy and withdrawal safety.