Detecting MISO and Opyn’s msg.value reuse vulnerability with Slither

Summary: On August 18, 2021, samczsun reported a critical vulnerability in SushiSwap's MISO smart contracts that put roughly 350 million USD (109 thousand ETH) at risk, an issue similar to an August 2020 attack on the Opyn codebase. Trail of Bits released two open-source Slither detectors, msg-value-loop and delegatecall-loop, which find the reuse of the same msg.value multiple times, used explicitly via msg.value in Opyn and implicitly via delegatecall in MISO.
Bottom line: Both bugs share one root cause: a payable function reuses a single msg.value across multiple recipients or calls, so the same ETH is counted more than once. The MISO report alone put roughly 350 million USD at risk, and the same pattern had already been exploited against Opyn a year earlier.

Read the original at Trail of Bits Blog ↗

Topics: Vulnerabilities & Patching
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