Vulnerability · Published Jul 27, 2026 · Assigned by GitHub_M

CVE-2026-64641Next.js: Denial of Service in App Router using Server Actions

High 8.2

In plain English

A high-severity security flaw in next.js from vercel. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.9% (higher than 59% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 4.0)8.2High

Exploit odds (30 days)0.9%top 41.5% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official description

Next.js is a React framework for building full-stack web applications. In versions 13.0.0 through 15.5.20 and 16.0.0 through 16.2.10, crafted requests targeting Next.js applications using App Router with at least one Server Action can lead to excessive CPU usage blocking processing of further requests in the same process. This issue has been fixed in versions 15.5.21 and 16.2.11.

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
npm	next	15.5.21	GHSA-m99w-x7hq-7vfj
npm	next	16.2.11	GHSA-m99w-x7hq-7vfj

Affected products (as reported)

Vendor	Product	Versions
vercel	next.js	>= 13.0.0, < 15.5.21>= 16.0.0, < 16.2.11

Weakness: CWE-834 · Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

References

https://github.com/vercel/next.js/security/advisories/GHSA-m99w-x7hq-7vfj x_refsource_CONFIRM
https://github.com/vercel/next.js/pull/96013 x_refsource_MISC
https://github.com/vercel/next.js/commit/019628571641dec57aaf349ba0c360e3964e6f12 x_refsource_MISC
https://github.com/vercel/next.js/releases/tag/v15.5.21 x_refsource_MISC
https://github.com/vercel/next.js/releases/tag/v16.2.11 x_refsource_MISC