CVE-2026-64648: Next.js: Response Body Cache Confusion for Requests Containing Bodies
Impact
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. Safe: fetch(new Request(init), init) Unsafe: fetch(new Request(init), aDifferentInit)
Workarounds
No workaround exists besides upgrading. Applications using Pages Router are not vulnerable.
Other sources
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.
— MITRE
Affected Software
Remediation
Event History
Frequently Asked Questions
What is the severity of CVE-2026-64648?
The severity of CVE-2026-64648 is rated as 55 on the CVSS scale, indicating a moderate risk level.
How do I fix CVE-2026-64648?
To mitigate CVE-2026-64648, ensure that your server-side `fetch` implementation correctly handles request bodies and responses to prevent unauthorized cache leaks.
What systems are affected by CVE-2026-64648?
CVE-2026-64648 affects applications built using next.js from the npm package.
What is the impact of CVE-2026-64648?
CVE-2026-64648 allows for the potential leakage of confidential data from `POST` request responses to unauthorized clients due to cached responses.
When was CVE-2026-64648 published?
CVE-2026-64648 was published on July 22, 2026.