Bonzo Lend exploited for $9M via oracle signature flaw on Hedera
In brief
- Bonzo Lend paused all withdrawals after attacker borrowed $9.05M via manipulated oracle signature.
- Exploit inflated 250 SAUCE tokens' value by 12 orders of magnitude in single transaction.
- Second wallet borrowed $1M; Bonzo treating as recovered pending white-hat contact.
- Supra oracle provider fixed verifier flaw; lending pool and Bonzo Points remain closed.
The exploit: zeroed inputs bypass signature verification
Bonzo Lend locked withdrawals after an oracle verifier accepted a proof containing a zeroed signature and public key. The attacker's submission had no valid oracle signature — the signature field was set to [0,0], and the referenced committee public key pointed to the mathematical identity point as well.
Supra's verifier sent those zero inputs to Hedera's pairing precompile. Because both points represented the mathematical identity, the precompile returned true. The verifier then treated that result as proof of a committee signature because it had not first rejected zero, identity, and off-subgroup inputs.
In essence, the system answered a cryptographic equation correctly but mistook the answer for authorization.
How $9M moved in seconds
Wallet A first deposited 250 SAUCE, worth only a few dollars. It then submitted a SAUCE/wHBAR price update that inflated the token's value by roughly 12 orders of magnitude. Eight seconds after the manipulated price reached the oracle's on-chain storage, the wallet borrowed 6.63 million USDC. It then borrowed 34.5 million wrapped HBAR, bringing the principal extracted to approximately $9.05 million.
A separate wallet borrowed roughly $1 million while the abnormal price remained live. That wallet contacted Bonzo, identified itself as a white-hat responder, and stated that it intended to return the funds. Bonzo counted roughly $1 million as recovered, though the funds had yet to be returned and the final tally was still unsettled.
Status and recovery
Bonzo reported that Supra fixed the verifier, but the lending pool remains closed. Bonzo Lend and Bonzo Points remained paused as of July 13. Liquidity providers remain unable to withdraw while Bonzo Finance Labs and the Bonzo Finance Foundation determine a recovery path.
Bonzo has yet to announce reimbursement, a reopening date, or user-facing withdrawal terms, leaving liquidity providers dependent on the recovery plan that comes next.
