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Authorization Bypass in Next.js Middleware

Critical
jackwilson323 published GHSA-f82v-jwr5-mffw Mar 21, 2025

Package

npm next (npm)

Affected versions

> 11.1.4 < 12.3.5
>14.0 <14.2.25
>15.0 <15.2.3
>= 13.0.0, < 13.5.9

Patched versions

12.3.5
14.2.25
15.2.3
13.5.9

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_)

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

CVE ID

CVE-2025-29927

Weaknesses

Credits