CVE-2025-66559: Taikoxyz Taiko-Mono

High severity, CVSS 8.0. EPSS: 0.3% chance of exploitation in the next 30 days.

Taiko Alethia is an Ethereum-equivalent, permissionless, based rollup designed to scale Ethereum without compromising its fundamental properties. In 2.3.1 and earlier, TaikoInbox._verifyBatches (packages/protocol/contracts/layer1/based/TaikoInbox.sol:627-678) advanced the local tid to whatever transition matched the current blockHash before knowing whether that batch would actually be verified. When the loop later broke (e.g., cooldown window not yet passed or transition invalidated), the function still wrote that newer tid into batches[lastVerifiedBatchId].verifiedTransitionId after decrementing batchId. Result: the last verified batch could end up pointing at a transition index from the next batch (often zeroed), corrupting the verified chain pointer.

Affected products

• Taikoxyz Taiko-Mono: up to and including 2.3.1

Published 2025-12-04. Last modified 2026-06-17.