In one of the most comprehensive hacks since Axie Infinity’s Ronin Bridge Side Chain in March, an exploit on the Nomad token bridge allowed attackers to rob the bridge of approximately $190 million.
“We are aware of the incident involving the Nomad token bridge. We are currently investigating and will provide updates when we have them,” Nomad tweeted Monday afternoon.
We are aware of the incident involving the Nomad token bridge. We are currently investigating and will provide updates when we have them.
The Nomad bridge is a protocol that allows users to move digital assets between different blockchains, including Avalanche (AVAX), Ethereum (ETH), Evmos (EVMOS), Milkomeda C1 and Moonbeam (GLMR).
Nomad TVL plunged when funds were lifted from the protocol. Picture: DeFi Lama.
While details from Nomad are scarce, some have pointed to a configuration error in one smart contract which Nomad uses to treat messages as cause, so that millions can be drained from Nomad’s liquidity pool.
“It all started when @officer_cia shared @spreekaway’s tweet in the ETHSecurity Telegram channel,” tweeted Sam Sun, a researcher at crypto investment firm Paradigm. “Although I had no idea what was going on at the time, just the volume of assets leaving the bridge was a definite bad sign.”
“It turns out that during a routine upgrade,” Sun continued. “The Nomad team initialized the trusted root to be 0x00. To be clear, using null values as initialization values is a common practice. Unfortunately, in this case it had a small side effect of automatically confirming every message.”
Sun likened what happened next to “a crazy free-for-all” because it took little technical know-how to exploit the exploit.
“You didn’t need to know about Solidity or Merkle Trees or anything like that,” Sun wrote. “All you had to do was find a transaction that worked, find/replace the other person’s address with yours, and then rebroadcast it.”
Equivalent blockchain security company Certificate reported it attackers can exploit the flaw by copying and pasting transactions. The firm added that people could exploit the upgrade “by copying the original hacker’s transaction data and replacing the original address with a personal one.”
🚨Explaining the Nomad bridge hack 🚨
All credit to @samczsun for doing the heavy lifting of diagnosing the exact vulnerability in his postmortem
How did we get the first decentralized looting of a 9-figure bridge in history? pic.twitter.com/v5u6mrKQv1
In this way, the bridge was drained of almost all its funds.
“Nomad’s bridge was owned similarly to Qubit’s QBridge,” tweeted a16z security engineer Matt Gleason. “An insecure configuration of the bridge caused a specific path to allow any transaction to be sent. The bug is inside Replica’s ‘process’ function.”
1/ Nomad’s bridge was owned in a similar way to Qubit’s QBridge. An insecure configuration of the bridge caused a certain path to allow any transaction sent. The error is inside the replica’s “process” function.
“The system will accept any message that it has never seen before and treat it as if it were real, meaning all you have to do is ask for all the bridge’s money and you will get it,” he added.
