GHSA-955p-x3mx-jcvp CVE-2026-64643
Next.js: Unauthenticated disclosure of internal Server Function endpoints
- Severity
- 0.0 / 10
- Medium · CVSS 4.0
- Exploit chance (EPSS)
- 0.51%
- Chance of exploitation in the next 30 days. Higher than 43.52% of scored vulnerabilities.
- Known exploited
- No
- Not in CISA's catalog
- Weakness
- CWE-201 Insertion of Sensitive Information Into Sent Data
- Fix
15.5.21- Upgrade next to this version or later
Description
Impact
In Next.js applications using App Router, Server Actions (use server) or use cache endpoints can be disclosed bypassing any authentication on the pages where these endpoints are usually used.
Server Action IDs can be disclosed to unauthenticated users via publicly served client artifacts (for example, static chunks containing action references).
Affected users are applications using App Router + Server Actions.
By itself, this disclosure is typically a recon/enumeration primitive; however, it can increase risk when combined with other weaknesses.
Workarounds
Never assume any authentication claims at the use cache or use server boundary. Always authenticate within the boundary.
Affected versions
npm
How to fix
Move to the fixed version or later with your package manager, update the lockfile, and run your tests. If the package only arrives through another dependency, upgrade that dependency first. If none of its releases pulls a fixed version yet, force the version with your package manager's override.
next npm → 15.5.21
- npm
npm install next@15.5.21- yarn
yarn add next@15.5.21- pnpm
pnpm add next@15.5.21
Severity breakdown
CVSS 4.0 0.0
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N
- Attack vector
- Network
- Attack complexity
- Low
- Attack requirements
- Present
- Privileges required
- None
- User interaction
- None
- Confidentiality (vulnerable system)
- Low
- Integrity (vulnerable system)
- None
- Availability (vulnerable system)
- None
- Confidentiality (subsequent systems)
- None
- Integrity (subsequent systems)
- None
- Availability (subsequent systems)
- None
CVSS 3.1 5.3
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
- Attack vector
- Network
- Attack complexity
- Low
- Privileges required
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- Low
- Integrity
- None
- Availability
- None
Weakness
CWE-201: Insertion of Sensitive Information Into Sent Data
The code transmits data to another actor, but a portion of the data includes sensitive information that should not be accessible to that actor.
How to prevent it
- Requirements: Specify which data in the software should be regarded as sensitive. Consider which types of users should have access to which types of data.
- Implementation: Ensure that any possibly sensitive data specified in the requirements is verified with designers to ensure that it is either a calculated risk or mitigated elsewhere. Any information that is not necessary to the functionality should be removed in order to lower both the overhead and the possibility of security sensitive data being sent.
- System Configuration: Setup default error messages so that unexpected errors do not disclose sensitive information.
- Architecture and Design: Compartmentalize the system to have "safe" areas where trust boundaries can be unambiguously drawn. Do not allow sensitive data to go outside of the trust boundary and always be careful when interfacing with a compartment outside of the safe area. Ensure that appropriate compartmentalization is built into the system design, and the compartmentalization allows for and reinforces privilege separation functionality. Architects and designers should rely on the principle of least privilege to decide the appropriate time to use privileges and the time to drop privileges.
References
Packages
Other links
- github.com/vercel/next.js/security/advisories/GHSA-955p-x3mx-jcvp
- github.com/vercel/next.js/commit/1b0c3ae912a3ad925c60065cc8d55b070fa8bcd3
- github.com/vercel/next.js/commit/ff12a6124e1504f17b62de948b8a553fdecaef7b
- github.com/vercel/next.js/releases/tag/v15.5.21
- github.com/vercel/next.js/releases/tag/v16.2.11
Timeline
- Published
- Last updated by the source
- Latest EPSS score
Related advisories
| Advisory | Severity | Why it's related |
|---|---|---|
| GHSA-673q-mjm6-r5xr Next.js: Unauthenticated Remote Code Execution in `use cache` functions returning typed arrays | Critical | Also affects next |
| GHSA-2464-fhr4-w9xw Next.js: Unauthenticated Remote Code Execution in Image Optimization API when SVG files are used | Critical | Also affects next |
| GHSA-p3m5-59mp-jv5r Next.js: Denial of Service in App Router using Server Actions | High | Also affects next |
| GHSA-3w37-wq28-93x7 Next.js: Pending `use cache` fill can leak Draft Mode content into regular responses and persisted pages | Medium | Also affects next |
| GHSA-4jqv-mc3x-m676 Next.js has cache poisoning of SSG and ISR pages in self-hosted applications | Medium | Also affects next |
| GHSA-39w2-rjm5-chcv Next.js has information disclosure in development server's Model Context Protocol endpoint | Medium | Also affects next |
| GHSA-f87g-xv8r-7p7x Next.js has information disclosure in App Router metadata image routes via dynamicParams bypass | Medium | Also affects next |
| GHSA-mcj8-r9mp-w47p Next.js has cache poisoning in SSG/ISR rendering that leads to cross-user content substitution and persistent denial of service | Medium | Also affects next |
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