# CVE-2026-64648: Vercel Next.js cache confusion in server-side fetch

Source: https://junglewise.ai/threats/cve-2026-64648-vercel-next-js-cache-confusion-in-server-side-fetch  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-07-27. Updated: 2026-07-27  
License: CC BY 4.0 with a link back

CVE-2026-64648 · Severity: medium · CVSS 4 · Published 2026-07-27

Next.js is a popular framework used to build web applications. A security flaw in its server-side data fetching mechanism could cause the system to accidentally serve sensitive data from one user's request to a different, unauthorized user. This occurs because the framework may incorrectly reuse cached responses even when the underlying request data is different, potentially leading to the exposure of private information.

Technologies: [next (npm)](https://junglewise.ai/threats/technologies/npm-next), [Vercel Next.js](https://junglewise.ai/threats/technologies/next-js). Vendors: [npm](https://junglewise.ai/threats/vendors/npm), [Vercel](https://junglewise.ai/threats/vendors/vercel).

## Quick answers

**Is CVE-2026-64648 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-64648 being exploited in the wild.

**How severe is CVE-2026-64648?** Medium severity, with a CVSS score of 4, published 27 July 2026.

**Which products and versions are affected?** next (npm) SEMVER:introduced=13.0.0,fixed=15.5.21; Vercel Next.js >= 13.0.0, < 15.5.21; >= 16.0.0, < 16.2.11.

**Is there a fix for CVE-2026-64648?** Yes. next (npm): upgrade to 15.5.21 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-64648 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-64648?** Check whether you run next (npm) or Vercel Next.js at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- next (npm): upgrade to 15.5.21 or later

  ```sh
  npm install next@15.5.21
  ```


## Technical details

A cache confusion vulnerability exists in Next.js App Router due to improper cache key generation for server-side fetch calls. When a fetch call is made using a Request object and a separate initialization object (init) that differs from the Request's own init, the framework may fail to distinguish between requests with different bodies. This results in the server returning a cached response body from a previous request to the same URL, even if the POST bodies were different. The vulnerability is classified as CWE-524 (Use of Cache Containing Sensitive Information) and has been patched in versions 15.5.21 and 16.2.11. Applications using the Pages Router are not affected.

## Affected products

- Vercel Next.js >= 13.0.0, < 15.5.21; >= 16.0.0, < 16.2.11

## Identifiers

- CVE-2026-64648
- GHSA-68g3-v927-f742

## Timeline

- 2026-07-21: advisory: GitHub Security Advisory published
- 2026-07-21: patched: Fixed in versions 15.5.21 and 16.2.11
- 2026-07-27: disclosed: CVE published to NVD

## References

- [https://github.com/vercel/next.js/commit/062f66700b52a5d6bba2c0605d55577ab7ad262c](https://github.com/vercel/next.js/commit/062f66700b52a5d6bba2c0605d55577ab7ad262c)
- [https://github.com/vercel/next.js/commit/73b94872bc343d09494b50394d8c08eb9fc8e56a](https://github.com/vercel/next.js/commit/73b94872bc343d09494b50394d8c08eb9fc8e56a)
- [https://github.com/vercel/next.js/releases/tag/v15.5.21](https://github.com/vercel/next.js/releases/tag/v15.5.21)
- [https://github.com/vercel/next.js/releases/tag/v16.2.11](https://github.com/vercel/next.js/releases/tag/v16.2.11)
- [https://github.com/vercel/next.js/security/advisories/GHSA-68g3-v927-f742](https://github.com/vercel/next.js/security/advisories/GHSA-68g3-v927-f742)

## Related threats

- [Vercel Next.js remote code execution in use cache functions](https://junglewise.ai/threats/next-js-unauthenticated-remote-code-execution-in-use-cache-functions-ac3e73d3)
- [Next.js denial of service in App Router with Server Actions](https://junglewise.ai/threats/cve-2026-94482-next-js-denial-of-service-in-app-router-using-server-actions)
- [Next.js unauthenticated remote code execution in Image Optimization API](https://junglewise.ai/threats/next-js-unauthenticated-remote-code-execution-in-image-optimization-api-f1b22a87)
- [Next.js information disclosure in Draft Mode via use cache](https://junglewise.ai/threats/cve-2026-94544-next-js-is-a-react-framework-for-building-full-stack-web)
- [Next.js Pages Router response cache key bypass](https://junglewise.ai/threats/cve-2026-94543-next-js-is-a-react-framework-for-building-full-stack-web)