What is the CVSS score of CVE-2025-66559?

CVE-2025-66559 has a CVSS 4.0 base score of 8.0 (High). CVSS vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:U. EPSS exploitation probability: 0.1%.

Which versions of Taiko Alethia are affected by CVE-2025-66559?

A critical logic flaw in Taiko's batch verification process (CVE-2025-66559) can corrupt the verified transaction chain pointer, potentially allowing invalid or malicious transactions to be accepted…

How to fix or mitigate CVE-2025-66559?

Within 24 hours: Assess whether your infrastructure directly operates Taiko validators, sequencers, or settlement nodes; if yes, escalate to engineering and prepare rollback procedures. Within 7 days: Monitor Taiko Foundation communications for patch availability and conduct impact analysis on dependent applications. Within 30 days: Deploy patched version immediately upon release, or if no patch emerges, evaluate migration to alternative rollup solutions or request formal risk acceptance from leadership.

Taiko Alethia CVE-2025-66559

EUVD-2025-201290 HIGH

Improper Validation of Array Index (CWE-129)

2025-12-04 security-advisories@github.com

Information Disclosure

8.0

CVSS 4.0 · GitHub Advisory

Severity by source

GitHub Advisory PRIMARY

8.0 HIGH

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:U

Primary rating from GitHub Advisory · only source for this CVE.

CVSS VectorGitHub Advisory

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:U

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Lifecycle Timeline

EUVD ID Assigned

Mar 15, 2026 - 16:35 euvd

EUVD-2025-201290

Analysis Generated

Mar 15, 2026 - 16:35 vuln.today

CVE Published

Dec 04, 2025 - 23:15 nvd

HIGH 8.0

DescriptionGitHub Advisory

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.