The same vulnerability, the same target, the second emergency shutdown in less than 30 days.
RetoSwap, a Monero-based P2P trading platform, urgently suspended all trading on June 17, 2026, after confirming that the Haveno protocol it relies on was under active exploitation. This marks the second attack on the Haveno protocol within a month. The first incident on May 20 resulted in the theft of 7,000 XMR worth approximately $2.7 million.
The team stressed that its own infrastructure was not compromised. The vulnerability lies within the Haveno protocol — an open-source trading framework that RetoSwap inherits. RetoSwap did not write the vulnerable code; it inherited it.
How the Exploit Works: Arbitrator Spoofing
In the May 20 attack, the attacker sent a fake, out-of-order acknowledgment message impersonating the arbitrator — a neutral third party in Haveno's 2-of-3 multisignature wallet system. This message caused the victim's client to overwrite the legitimate arbitrator's address with the hacker's address. Before the victim's funds were even deposited into the multisig wallet, the hacker obtained two out of three wallet keys.
Plainly put: the attacker posed as the referee before the game started and rigged the outcome before any money entered the pot.
The attack mainly affected large cryptocurrency transactions; fiat trading parties were unaffected. This was by design — the attacker mapped the protocol's architecture, identified the pathway handling large-volume crypto swaps, and targeted it.
Second Attack: Patch Not Enough
After May 20, RetoSwap applied a fix — mandatory upgrade to client version 2.0.0 and banning attacker onion addresses. Haveno lead developer woodser identified a straightforward prevention: check that the multisig wallet is already created before updating the arbitrator's address. A GitHub pull request was opened.
But the June 17 suspension signals that attackers found a way to re-exploit the protocol — whether through a new vector or residual exposure of the same vulnerability. RetoSwap confirmed losses again limited to large crypto-asset transactions. The team is evaluating recovery options for affected traders but has not set a timeline for resuming trading.
Recovering stolen XMR is nearly impossible. Monero's privacy-first design — the same feature that makes it valuable — protects attackers as effectively as legitimate users. PeckShield can flag the incident, but once funds are moved, they are effectively gone.
What Users Should Do Now
RetoSwap has issued four security steps: back up your wallet folder immediately (Linux: ~/.local/share/Haveno-reto/xmr_mainnet/wallet; macOS: ~/Library/Application Support/Haveno-reto/xmr_mainnet/wallet); do not attempt trades until the protocol fix is confirmed; upgrade to client version 2.0.0 or higher before the platform reopens; and always verify arbitrator communications in P2P trades.
The broader lesson: RetoSwap didn't write the buggy code, but it inherited a broken protocol. Every platform built on Haveno carries the same inherited risk — until the core protocol undergoes a complete independent security audit.