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Next.js vulnerable to cache poisoning in React Server Component responses

Moderate severity GitHub Reviewed Published May 6, 2026 in vercel/next.js • Updated May 14, 2026

Package

npm next (npm)

Affected versions

>= 14.2.0, < 15.5.16
>= 16.0.0, < 16.2.5

Patched versions

15.5.16
16.2.5

Description

Impact

Applications using React Server Components can be vulnerable to cache poisoning when shared caches do not correctly partition response variants. Under affected conditions, an attacker can cause an RSC response to be served from the original URL and poison shared cache entries so later visitors receive component payloads instead of the expected HTML.

Fix

We now validate and interpret RSC request headers consistently across request classification and rendering, and we enforce the intended cache-busting behavior so RSC payloads are not unexpectedly served from the original URL.

Workarounds

If you cannot upgrade immediately, ensure your CDN or reverse proxy keys on the relevant RSC request headers and honors Vary, or disable shared caching for affected App Router and RSC responses.

References

@timneutkens timneutkens published to vercel/next.js May 6, 2026
Published to the GitHub Advisory Database May 11, 2026
Reviewed May 11, 2026
Published by the National Vulnerability Database May 13, 2026
Last updated May 14, 2026

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
High
Privileges required
None
User interaction
None
Scope
Changed
Confidentiality
None
Integrity
Low
Availability
Low

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:H/PR:N/UI:N/S:C/C:N/I:L/A:L

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.
(16th percentile)

Weaknesses

Interpretation Conflict

Product A handles inputs or steps differently than Product B, which causes A to perform incorrect actions based on its perception of B's state. Learn more on MITRE.

CVE ID

CVE-2026-44576

GHSA ID

GHSA-wfc6-r584-vfw7

Source code

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