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VulnerabilityPublished Updated

CVE-2025-30218: vercel next.js · Information Exposure

Affects vercel next.jsSource CVE Database V5

0

Mentioned vulnerabilities

Not known to be exploited · CVSS 1.7 Low · fixed in 12.3.6 : update vercel next.js when convenient.

Data as of 26 Oct 2026, 14:05 UTC

CVSS 4.0 base score
1.7Low
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.4% chance of exploitation in 30 days – higher than 37% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 12.3.6
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

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 2 Apr 2025

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponised: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

What to do

Affected software

ProductAffectedFixed in
vercel next.jsAffected
  • 12.3.5 – 15.2.3
4 affected builds
Fixed in–

AI-suggested

The primary mitigation is to upgrade all affected Next.js instances to the patched versions: 12.3.6, 13.5.10, 14.2.26, or 15.2.4, depending on the version in use. Beyond upgrading, organizations should audit their middleware fetch requests to third-party domains to ensure no sensitive headers or internal identifiers are unintentionally forwarded. Implement strict header filtering or sanitization in middleware to prevent leakage of internal tracking headers to external services. Additionally, review third-party integrations to assess the necessity and security posture of external endpoints receiving requests from middleware. Employ network monitoring to detect unusual outbound requests carrying internal headers. Finally, incorporate this vulnerability into regular security assessments and developer training to raise awareness about secure middleware practices in Next.js applications.

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.

References

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