# CVE-2025-30218: Next.js may leak x-middleware-subrequest-id to external hosts

> Next.js leaks internal middleware subrequest IDs to external hosts during fetch requests, potentially exposing sensitive internal state information.

- **Severity:** Low 1.7 (`CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/VI:N/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:** Yes
- **Published:** 2 Apr 2025
- **Updated:** 13 Oct 2025
- **Also known as:** CLEANSTART-2026-HK16178, GHSA-223j-4rm8-mrmf

## What is CVE-2025-30218?

CVE-2025-30218 is a low-severity vulnerability in Vercel Next.js, published on 2 Apr 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Next.js is a React framework for building full-stack web applications. To mitigate CVE-2025-29927, Next.js validated the x-middleware-subrequest-id which persisted across multiple incoming requests. However, this subrequest ID is sent to all requests, even if the destination is not the same host as the Next.js application. Initiating a fetch request to a third-party within Middleware will send the x-middleware-subrequest-id to that third party. This vulnerability is fixed in 12.3.6, 13.5.10, 14.2.26, and 15.2.4.

Weakness: CWE-200 (Exposure of Sensitive Information to an Unauthorized Actor)

## Which versions are affected by CVE-2025-30218?

8 open source packages ship an affected version, including next. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `next` | npm | From 12.3.5 | 12.3.6 |
| `next` | npm | From 12.3.5 | 12.3.6 |
| `next` | npm | From 13.5.9 | 13.5.10 |
| `next` | npm | From 13.5.9 | 13.5.10 |
| `next` | npm | From 14.2.25 | 14.2.26 |
| `next` | npm | From 14.2.25 | 14.2.26 |
| `next` | npm | From 15.2.3 | 15.2.4 |
| `next` | npm | From 15.2.3 | 15.2.4 |

Products: Vercel Next.js.

## How do I fix CVE-2025-30218?

Upgrade next to a fixed version for your release line: 12.3.6, 13.5.10, 14.2.26 or 15.2.4.

## Is CVE-2025-30218 being exploited?

There is no known exploitation of CVE-2025-30218 in the wild and no public exploit code.

## Other vulnerabilities in Vercel Next.js

- [CVE-2025-29927](https://insights.sbomify.com/CVE-2025-29927/): Authorization Bypass in Next.js Middleware (critical 9.1)
- [CVE-2026-44578](https://insights.sbomify.com/CVE-2026-44578/): Next.js: Server-side request forgery in applications using WebSocket upgrades (high 8.6)
- [CVE-2026-94483](https://insights.sbomify.com/CVE-2026-94483/): Next.js: Server-Side Request Forgery in Image Optimization (high 8.3)
- [CVE-2026-64642](https://insights.sbomify.com/CVE-2026-64642/): Next.js: Middleware / Proxy bypass in App Router applications using Turbopack and single locale (high 8.3)
- [CVE-2026-64645](https://insights.sbomify.com/CVE-2026-64645/): Next.js: Server-Side Request Forgery in rewrites via attacker-controlled destination hostname (high 8.3)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-30218 and fix it if it is affected.

What it is: CVE-2025-30218 is a low-severity vulnerability in Vercel Next.js, published on 2 Apr 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-2025-30218 in the wild and no public exploit code.

Affected packages and fixed versions:
- next (npm): affected from 12.3.5; fixed in 12.3.6
- next (npm): affected from 12.3.5; fixed in 12.3.6
- next (npm): affected from 13.5.9; fixed in 13.5.10
- next (npm): affected from 13.5.9; fixed in 13.5.10
- next (npm): affected from 14.2.25; fixed in 14.2.26
- next (npm): affected from 14.2.25; fixed in 14.2.26
- next (npm): affected from 15.2.3; fixed in 15.2.4
- next (npm): affected from 15.2.3; fixed in 15.2.4

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-2025-30218/ (Markdown: https://insights.sbomify.com/CVE-2025-30218/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-30218
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-30218
- OSV: https://osv.dev/vulnerability/CVE-2025-30218

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-30218/
Summaries are generated and may contain mistakes; the official description above is the record.