On August 13, 2023, Zunami Protocol — a decentralized finance platform built on Ethereum — suffered a devastating flash loan attack that siphoned approximately $2.16 million from its vaults. The post-mortem, published on August 31, 2023, revealed a subtle but catastrophic vulnerability in the protocol’s price caching mechanism, one that escaped multiple professional audits. With Bitcoin trading around $25,931 and Ethereum at $1,645 at the time, the exploit sent ripples through the DeFi community already on edge from a summer of high-profile breaches.
The Exploit Mechanics
The attack exploited two separate but related vulnerabilities in Zunami’s price caching system. The first target was Zunami ETH (zETH), where the attacker drained 26 WETH. The second, far more damaging strike targeted Zunami Stable (UZD), extracting a staggering 1,178 WETH. Both attacks hinged on the same fundamental flaw: the protocol cached inflated LP token prices for the duration of an entire block, creating a window exploitable through flash loans.
The root cause traced back to the MIMCurveStakeDAO strategy, introduced in a protocol update. This strategy calculated LP prices using the balance and price of SDT tokens held within the strategy contract. An attacker could manipulate this calculation by donating SDT tokens to the strategy, artificially inflating the cached price. Because the inflated price persisted for the entire block, the attacker could execute a series of reverse operations — borrowing via flash loan, manipulating the price, extracting value at the inflated rate, and repaying the loan — all within a single transaction.
Affected Systems
The vulnerability specifically affected the ElasticERC20 implementation in Zunami Stable v1.1. Price caching was partially implemented in v1.0 and audited by Ackee Blockchain. However, in v1.1, the caching was extended to critical functions including totalSupply, balanceOf, and allowance. This expansion meant that other contracts calling balanceOf would receive the manipulated cached price — a design decision that introduced the attack vector.
Crucially, the v1.1 update was launched without any audit. It was only later, for the v1.2 launch, that HashEx conducted an audit on October 29, 2023 — but even that review failed to identify the cached function attack vector. The MIMCurveStakeDAO strategy itself had been audited by HashEx prior to launch, yet the exploit possibility slipped through.
The Mitigation Strategy
Following the exploit, the Zunami team took several corrective actions. The vulnerable MIMCurveStakeDAO strategy was disabled, and the protocol paused deposits while a thorough review was conducted. The post-mortem analysis, contributed to by Ackee Blockchain, identified the specific code paths that enabled the attack.
Key mitigations implemented included removing global price caching from view functions that could be called by external contracts, implementing real-time price calculations for critical operations, and establishing a requirement for comprehensive audits before any strategy contract modifications. The protocol also moved toward multi-auditor reviews, recognizing that no single audit firm catches every vulnerability.
Lessons Learned
The Zunami exploit carries several critical lessons for the DeFi ecosystem. First, no code change is too small for an audit. The v1.1 update that extended price caching may have seemed incremental, but it fundamentally changed the attack surface. Second, price oracles and caching mechanisms demand extreme scrutiny. Any system that allows price data to be influenced by user actions within the same transaction creates flash loan attack vectors. Third, audits are necessary but not sufficient. The fact that both Ackee Blockchain and HashEx missed this vulnerability demonstrates that even professional audits have blind spots.
For DeFi users, the incident reinforces the importance of monitoring which protocol versions are actively deployed and whether recent updates have been audited. Protocols that ship unaudited updates to core financial logic represent elevated risk, regardless of their track record.
User Action Required
Users who had funds in Zunami Protocol vaults at the time of the August 13 exploit should verify whether they were affected. Check transaction histories for any unexpected withdrawals from zETH or UZD pools. For ongoing DeFi participation, always verify that the protocol version you are interacting with has been audited, and consider diversifying across multiple protocols to limit exposure to single-point failures. With the crypto market showing Bitcoin at approximately $25,931 and Ethereum around $1,645, the broader market context suggests cautious optimism — but protocol-level risks remain ever-present.
Disclaimer: This article is for informational purposes only and does not constitute financial advice. Always conduct your own research before interacting with any DeFi protocol.
auditors tested each function in isolation and missed the cross-function state change. this is why audit reports are theater without game theoretic analysis of composability
cached lp prices for an entire block is just asking for a flash loan drain. the 2.16m was basically free money for the attacker
MIMCurveStakeDAO strategy passing governance without security review is peak DAO theater. who voted yes and did anyone actually read the integration spec before approving
caching LP prices for an entire block is like leaving your front door open and being surprised when someone walks in
audited 3 times and still shipped with cached LP prices per block. at some point the audit industry needs to admit their methodology is broken
the MIMCurveStakeDAO strategy was the root cause? so basically one unaudited strategy update compromised the entire vault system. how does that pass governance
cached prices for an entire block is such an obvious vector. surprised it survived multiple audits honestly
audits are theater sometimes. the auditor checks the code you show them, not the code you deploy after the audit
cached LP prices for a full block is just asking to get exploited. any attacker with flash loan access can manipulate that window
1,178 WETH from UZD alone. the zETH drain of 26 WETH was probably just a test run before the main attack
26 WETH test run then 1178 WETH main hit. classic two stage exploit pattern, the first one was basically the attacker verifying the path worked
26 WETH was definitely a probe. the real question is why the protocol didnt pause after the first hit
hazel_nut the protocol not pausing after the 26 WETH probe is the real failure. that was a free warning shot and they ignored it
Lev K. exactly. 26 weth was a free warning shot and nobody paused. 1178 weth later and they finally wake up
Lev K. 26 WETH as a probe and nobody paused. the second hit for 1178 WETH was completely preventable if the team had monitoring on the first transaction
an unaudited strategy update passing governance is a governance failure. who approved that without a security review
the MIMCurveStakeDAO strategy passed governance without a security review? who was voting on these proposals and why did nobody flag an unaudited strategy update
governance_noob exactly. the DAO voted yes on a strategy called MIMCurveStakeDAO and nobody thought to ask if integrating MIM into a curve staking wrapper needed extra review. governance theater
2.16M gone because prices were cached for one block too long. the fix is literally just updating prices per-transaction. costs like 30k gas
rekt_tax_deduction 30k gas for per-tx price updates vs 2.16M drained. the cost-benefit analysis is not even close. protocols that still cache prices per block are asking for it
caching LP prices for a full block is the kind of thing that survives audits because auditors check logic not game theory. flash loans make any stale price exploitable
MIMCurveStakeDAO strategy passed governance without security review. an unaudited strategy update compromised the entire vault. governance is theater without technical review
oracle_delay_ 1178 WETH drained from a single strategy. the attacker basically borrowed the exploit cost from the protocol itself via flash loan. zero capital required
caching LP token prices for an entire block is asking to get flash-loaned. the MIMCurveStakeDAO strategy was a ticking bomb from deployment
auditors missed this because they tested each function in isolation. the vulnerability only appeared when you chained the price cache with flash loan entry and exit in one tx
Tomoko S. chaining price cache with flash loan entry and exit is exactly the attack vector every auditor should test but most dont. state changes across function boundaries are invisible in isolation