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Authorization Bypass in Next.js Middleware

Critical severity GitHub Reviewed Published Mar 21, 2025 in vercel/next.js • Updated Oct 13, 2025

Package

npm next (npm)

Affected versions

>= 13.0.0, < 13.5.9
>= 14.0.0, < 14.2.25
>= 15.0.0, < 15.2.3
>= 11.1.4, < 12.3.5

Patched versions

13.5.9
14.2.25
15.2.3
12.3.5

Description

Impact

It is possible to bypass authorization checks within a Next.js application, if the authorization check occurs in middleware.

Patches

  • For Next.js 15.x, this issue is fixed in 15.2.3
  • For Next.js 14.x, this issue is fixed in 14.2.25
  • For Next.js 13.x, this issue is fixed in 13.5.9
  • For Next.js 12.x, this issue is fixed in 12.3.5
  • For Next.js 11.x, consult the below workaround.

Note: Next.js deployments hosted on Vercel are automatically protected against this vulnerability.

Workaround

If patching to a safe version is infeasible, we recommend that you prevent external user requests which contain the x-middleware-subrequest header from reaching your Next.js application.

Credits

  • Allam Rachid (zhero;)
  • Allam Yasser (inzo_)

References

@ghost ghost published to vercel/next.js Mar 21, 2025
Published by the National Vulnerability Database Mar 21, 2025
Published to the GitHub Advisory Database Mar 21, 2025
Reviewed Mar 21, 2025
Last updated Oct 13, 2025

Severity

Critical

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
None

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

EPSS score

Exploit Prediction Scoring System (EPSS)

This score estimates the probability of this vulnerability being exploited within the next 30 days. Data provided by FIRST.
(100th percentile)

Weaknesses

Improper Authorization

The product does not perform or incorrectly performs an authorization check when an actor attempts to access a resource or perform an action. Learn more on MITRE.

Incorrect Authorization

The product performs an authorization check when an actor attempts to access a resource or perform an action, but it does not correctly perform the check. Learn more on MITRE.

CVE ID

CVE-2025-29927

GHSA ID

GHSA-f82v-jwr5-mffw

Source code

Credits

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