🛡️ CVE-2025-30218 — next

🟡 CVSS 5.9 — Medium ✅ No Known Exploit CWE-200 NVD
5.9
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

Next.js may leak x-middleware-subrequest-id to external hosts

Summary

In the process of remediating [CVE-2025-29927](https://github.com/advisories/GHSA-f82v-jwr5-mffw), we looked at other possible exploits of Middleware. We independently verified this low severity vulnerability in parallel with two reports from independent researchers.

Learn more [here](https://vercel.com/changelog/cve-2025-30218-5DREmEH765PoeAsrNNQj3O).

Credit

Thank you to Jinseo Kim [kjsman](https://hackerone.com/kjsman?type=user) and [RyotaK](https://hackerone.com/ryotak?type=user) (GMO Flatt Security Inc.) with [takumi-san.ai](https://takumi-san.ai) for the responsible disclosure. These researchers were awarded as part of our bug bounty program.

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is high, an attacker needs no privileges on the target. No user interaction is required. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality high, integrity none, availability none.

Weakness class

CVE-2025-30218 is classified as CWE-200: Exposure of Sensitive Information. Information that should stay internal is disclosed to someone who is not authorised to see it.

Affected software

CVE-2025-30218 is recorded against 2 packages.

  • next
  • next.js

Timeline and source

Published on 2 April 2025 and last revised on 13 October 2025. No public exploit is currently recorded for this entry. Record sourced from NVD.

References

github.com (Web)
nvd.nist.gov (Advisory)
github.com (Package)
vercel.com (Web)

Details

Severity LOW
CVSS Score 5.9
CVSS Vector CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
CWE CWE-200
Public Exploit ✅ No
Source NVD
Published 2025-04-02
Updated 2026-08-12
Modified 2025-10-13
Fix URL N/A

Affected Packages

Software From version Fixed in
next — —
next.js — —

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