DeFi lending protocol Moonwell hit with $1.8 million bad debt after oracle misconfiguration

DeFi lending protocol Moonwell said it incurred approximately $1.78 million in bad debt after a configuration error caused its oracle to misprice Coinbase Wrapped ETH (cbETH), triggering a wave of liquidations on its Base market.

Moonwell is a decentralized, overcollateralized lending and borrowing protocol originally built on Moonbeam and now active on networks like Base and Optimism, allowing users to supply assets such as USDC to earn yield or borrow against crypto collateral through onchain money markets.

Post-mortem

The Feb. 15 incident occurred when governance proposal MIP-X43 was executed, enabling Chainlink OEV wrapper contracts across core markets on Base and Optimism. According to a post-mortem published on Moonwell’s governance forum on Tuesday, one oracle configuration incorrectly derived the USD value of cbETH by using only the raw cbETH/ETH exchange rate rather than multiplying it by the ETH/USD price feed.

As a result, cbETH was reported at approximately $1.12 — reflecting the cbETH/ETH ratio — instead of its intended market value of roughly $2,200.

Liquidation bots immediately targeted cbETH-backed positions. Because the system believed cbETH was worth just over $1, liquidators were able to repay minimal amounts of debt to seize large amounts of collateral.

In total, 1,096.317 cbETH was liquidated, leaving the protocol with $1,779,044.83 in bad debt across multiple assets, the majority denominated in cbETH.

Moonwell said its monitoring systems detected the discrepancy within minutes. To stem the bleed, the protocol reduced both supply and borrow caps for the affected cbETH Core Market on Base to 0.01, preventing new borrows and additional collateral deposits. No other markets on Base or OP Mainnet were affected, the team said.

However, correcting the oracle required a governance vote and timelock process, meaning liquidations continued until the configuration could be formally patched. A new governance proposal is slated to address that error.

AI-assistance scrutinized

The episode has drawn attention beyond the financial loss because the pull request associated with the configuration change shows commits co-authored by Claude Opus 4.6, an advanced AI model. Smart contract auditor “pashov” noted on X that the vulnerable code was written with AI assistance, prompting some observers to describe the incident as a potential first major exploit linked to “vibe-coded” Solidity.

SlowMist founder Cos said the issue stemmed from a very low-level error in the oracle price feed formula rather than a novel smart contract vulnerability. Other experts echoed that distinction. Mikko Ohtamaa, co-founder of Trading Protocol, said the problem was a configuration mistake that could have been made by a human developer and argued that proper integration tests and price sanity checks should have caught it regardless of authorship.

Moonwell has not attributed the incident specifically to AI-generated code. The Block reached out for comment.

The cbETH incident marks the latest in a series of oracle-related disruptions for Moonwell.

In October 2025, a Chainlink pricing discrepancy involving AERO, VIRTUAL, and MORPHO resulted in more than $12 million in liquidations and $1.7 million in bad debt. In November, a wrsETH oracle malfunction left the protocol with roughly $3.7 million in bad debt after distorted pricing fed through a market-based exchange rate.

Oracle mishaps are not uncommon in decentralized finance. The Block has previously reported on similar oracle missteps, including an April 2025 incident at Term Finance where a configuration error triggered faulty liquidations and roughly $1.6 million in losses, with about $1 million later recovered.