Executive brief
Next.js is a popular framework used to build and host web applications. A vulnerability in how the framework handles specific web requests can allow an attacker to overwhelm the server's processor. This results in a denial-of-service condition where the website becomes unresponsive to legitimate users, potentially causing business downtime and operational disruption.
Technical details
A denial of service (DoS) vulnerability exists in Next.js due to excessive iteration (CWE-834) when processing crafted requests. The issue resides in the App Router component when at least one Server Action is defined. An unauthenticated remote attacker can send specially crafted requests that trigger high CPU utilization, blocking the event loop and preventing the process from handling subsequent requests. The vulnerability affects versions 13.0.0 through 15.5.20 and 16.0.0 through 16.2.10. It has been remediated in versions 15.5.21 and 16.2.11 by improving the validation performance of Multi-Page Application (MPA) form submissions.
Affected products
- Vercel Next.js 13.0.0 - 15.5.20, 16.0.0 - 16.2.10
Timeline
- 2026-07-21: patched: Fixes released in v15.5.21 and v16.2.11
- 2026-07-21: advisory: GitHub Security Advisory GHSA-m99w-x7hq-7vfj published
- 2026-07-27: disclosed: CVE-2026-64641 published to NVD
References
- https://github.com/vercel/next.js/commit/019628571641dec57aaf349ba0c360e3964e6f12
- https://github.com/vercel/next.js/pull/96013
- 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/security/advisories/GHSA-m99w-x7hq-7vfj