# CVE-2025-66559: Taiko Alethia Pacaya inbox verification pointer corruption

> Attackers can corrupt verified chain pointers in Taiko Alethia by exploiting batch verification logic, compromising rollup integrity.

- **Severity:** High 8.0 (`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`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 4 Dec 2025
- **Updated:** 5 Dec 2025
- **Also known as:** GHSA-5mxh-r33p-6h5x

## What is CVE-2025-66559?

CVE-2025-66559 is a high-severity vulnerability in taikoxyz taiko-mono, published on 4 Dec 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

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.

Weakness: CWE-129 (Improper Validation of Array Index)

## Which versions are affected by CVE-2025-66559?


## How do I fix CVE-2025-66559?

No fix has been published for CVE-2025-66559 yet. Limit exposure of the affected software until one is available.

## Is CVE-2025-66559 being exploited?

There is no known exploitation of CVE-2025-66559 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-66559 and fix it if it is affected.

What it is: CVE-2025-66559 is a high-severity vulnerability in taikoxyz taiko-mono, published on 4 Dec 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2025-66559 in the wild and no public exploit code.

Affected product: taikoxyz taiko-mono. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2025-66559/ (Markdown: https://insights.sbomify.com/CVE-2025-66559/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-66559
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-66559
- OSV: https://osv.dev/vulnerability/CVE-2025-66559

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From sbomify Insights: https://insights.sbomify.com/CVE-2025-66559/
Summaries are generated and may contain mistakes; the official description above is the record.