The Incident: What Happened to Ekubo?
On May 6, 2026, Ekubo Protocol (a major liquidity layer) faced a $1.4M exploit. While the core liquidity remained safe, the vulnerability resided in the EVM extension router.
The attacker exploited a flaw in the Payment Callback logic, manipulating token transfers from users who had granted maximum approvals to the contract. This wasn't a flaw in the AMM math itself, but a failure in access control and state validation during cross-chain interactions.
The Solution: Active Invariant Monitoring
Post-mortem audits are great, but they don't bring back the funds. As a security researcher, I believe the future of DeFi security lies in Active Sentinel Agents—tools that monitor protocol invariants in real-time and trigger defensive actions.
To address this, I've updated my project, Sentinel-Rhea, to support multi-chain monitoring (EVM + Starknet).
- The Strategy Our agent doesn't just check if a hack happened; it checks if the rules of the protocol are still being followed.
For EVM (Mantle): We monitor the Assets-to-Shares ratio to detect "Ghost Debt".
For Starknet (Ekubo Core): We monitor pool reserves and "Flash Accounting" deltas.
- Implementation in Clojure Why Clojure? Its concurrency model and functional purity make it ideal for high-speed blockchain polling. Here is how we implemented a resilient, multi-chain watcher:
Clojure
;; Resilient Starknet RPC call with failover logic
(defn starknet-call
:body (json/generate-string
{:jsonrpc "2.0"
:method "starknet_call"
:params [{:contract_address contract
:entry_point_selector selector
:calldata calldata}
"latest"]
:id 1}">contract selector calldata
:content-type :json
:as :json})]
(if (= (:status response) 200)
(get-in response [:body :result])
(handle-failover)))
(catch Exception e
(log-error "RPC Failure" (.getMessage e)))))
- Handling Public RPC Challenges During development, we faced 403 Forbidden errors and Cloudflare blocks from public Starknet nodes. A production-grade sentinel must be resilient. We implemented:
User-Agent Masking to bypass basic filters.
Exception Handling to prevent agent crashes during network congestion.
Failover Logic to maintain monitoring even when specific nodes are unstable.
Conclusion
The Ekubo exploit is a reminder that the attack surface in DeFi is constantly evolving. By combining deep audit knowledge with automated monitoring tools, we can move from reactive to proactive security.
Check out the full source code and my research here: 👉 https://github.com/rdin777/sentinel-rhea