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Next Server Actions Source Code Exposure

Moderate severity GitHub Reviewed Published Dec 11, 2025 in vercel/next.js

Package

npmnext (npm)

Affected versions

>= 15.0.0-canary.0, < 15.0.6
>= 15.1.1-canary.0, < 15.1.10
>= 15.2.0-canary.0, < 15.2.7
>= 15.3.0-canary.0, < 15.3.7
>= 15.4.0-canary.0, < 15.4.9
>= 15.5.1-canary.0, < 15.5.8
>= 15.6.0-canary.0, < 15.6.0-canary.59
>= 16.0.0-beta.0, < 16.0.9
>= 16.1.0-canary.0, < 16.1.0-canary.17

Patched versions

15.0.6
15.1.10
15.2.7
15.3.7
15.4.9
15.5.8
15.6.0-canary.59
16.0.9
16.1.0-canary.17

Description

A vulnerability affects certain React packages for versions 19.0.0, 19.0.1, 19.1.0, 19.1.1, 19.1.2, 19.2.0, and 19.2.1 and frameworks that use the affected packages, including Next.js 15.x and 16.x using the App Router. The issue is tracked upstream as CVE-2025-55183.

A malicious HTTP request can be crafted and sent to any App Router endpoint that can return the compiled source code of Server Functions. This could reveal business logic, but would not expose secrets unless they were hardcoded directly into Server Function code.

References

@feedthejimfeedthejim published to vercel/next.js Dec 11, 2025
Published to the GitHub Advisory Database Dec 11, 2025
Reviewed Dec 11, 2025

Severity

Moderate

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
Low
Integrity
None
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:L/I:N/A:N

EPSS score

Weaknesses

Exposure of Sensitive System Information to an Unauthorized Control Sphere

The product does not properly prevent sensitive system-level information from being accessed by unauthorized actors who do not have the same level of access to the underlying system as the product does. Learn more on MITRE.

Deserialization of Untrusted Data

The product deserializes untrusted data without sufficiently ensuring that the resulting data will be valid. Learn more on MITRE.

Dependency on Vulnerable Third-Party Component

The product has a dependency on a third-party component that contains one or more known vulnerabilities. Learn more on MITRE.

CVE ID

No known CVE

GHSA ID

GHSA-w37m-7fhw-fmv9

Source code

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