CVE-2025-29927Public exploitNetwork attack vector

Authorization bypass via trusted internal request header

Published Mar 21, 2025 · Updated Apr 8, 2025

Authorization bypass in affected Next.js releases allows remote attackers to access routes protected only by Middleware. The router trusts an externally supplied x-middleware-subrequest header as an internal recursion marker and skips Middleware execution. The application must be self-hosted with authorization enforced only in Middleware; static exports and deployments on Vercel, Netlify, or Cloudflare Workers are not affected.

CVSS severity9.1
Critical
EPSS probability99.22%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Authorization bypass in affected Next.js releases allows remote attackers to access routes protected only by Middleware. The router trusts an externally supplied x-middleware-subrequest header as an internal recursion marker and skips Middleware execution. The application must be self-hosted with authorization enforced only in Middleware; static exports and deployments on Vercel, Netlify, or Cloudflare Workers are not affected.

The record

CVE
CVE-2025-29927
Published
Mar 21, 2025
Updated
Apr 8, 2025
Vendor
Vercel
Product
Next.js
Classifications
CWE-285, CWE-863, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 21, 2025CVE publishedPublication date reported by the CVE source.
  2. Apr 8, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=>= 11.1.4, < 12.3.5
  2. Affected versionversion=>= 13.0.0, < 13.5.9
  3. Affected versionversion=>= 14.0.0, < 14.2.25
  4. Affected versionversion=>= 15.0.0, < 15.2.3

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Vercel · Next.jsversion=>= 11.1.4, < 12.3.5; version=>= 13.0.0, < 13.5.9; version=>= 14.0.0, < 14.2.25; version=>= 15.0.0, < 15.2.3

Published CVSS scores

9.1GitHubCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-285Improper Authorization
CWE-863Incorrect Authorization
T1190Exploit Public-Facing Application

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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