Vercel Next.js up to 15.5.20/16.2.10 Server-side Fetch Cache fetch init information disclosure

Summaryinfo

A vulnerability marked as problematic has been reported in Vercel Next.js up to 15.5.20/16.2.10. The impacted element is the function fetch of the component Server-side Fetch Cache. The manipulation of the argument init leads to information disclosure. This vulnerability is referenced as CVE-2026-64648. Remote exploitation of the attack is possible. No exploit is available.

Detailsinfo

A vulnerability, which was classified as problematic, has been found in Vercel Next.js up to 15.5.20/16.2.10. This issue affects the function fetch of the component Server-side Fetch Cache. The manipulation of the argument init with an unknown input leads to a information disclosure vulnerability. Using CWE to declare the problem leads to CWE-200. The product exposes sensitive information to an actor that is not explicitly authorized to have access to that information. Impacted is confidentiality. The summary by CVE is:

Next.js is a React framework for building full-stack web applications. In versions 12.0.0 through 15.5.20 and 16.0.0 through 16.2.10, a server-side fetch with a request body may return a cached response body from a different request to the same URL but different body. Confidential data in the POST's response body would then leak to unauthorized requests. Though the request itself will not be deduped. This only applies to fetch calls with a request that has a different init than the one passed to fetch. A safe request would be: fetch(new Request(init), init). An unsafe request would be: fetch(new Request(init), aDifferentInit). This issue has been fixed in versions 15.5.21 and 16.2.11.

It is possible to read the advisory at github.com. The identification of this vulnerability is CVE-2026-64648 since 07/20/2026. The exploitation is known to be easy. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. Technical details of the vulnerability are known, but there is no available exploit. The attack technique deployed by this issue is T1592 according to MITRE ATT&CK.

Upgrading to version 15.5.21 or 16.2.11 eliminates this vulnerability.

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Productinfo

Type

• JavaScript Library

Vendor

• Vercel

Name

• Next.js

Version

• 15.5.0
• 15.5.1
• 15.5.2
• 15.5.3
• 15.5.4
• 15.5.5
• 15.5.6
• 15.5.7
• 15.5.8
• 15.5.9
• 15.5.10
• 15.5.11
• 15.5.12
• 15.5.13
• 15.5.14
• 15.5.15
• 15.5.16
• 15.5.17
• 15.5.18
• 15.5.19
• 15.5.20
• 16.2.0
• 16.2.1
• 16.2.2
• 16.2.3
• 16.2.4
• 16.2.5
• 16.2.6
• 16.2.7
• 16.2.8
• 16.2.9
• 16.2.10

Website

• Product: https://github.com/vercel/next.js/

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