CVE-2026-64641: Next Denial of Service Vulnerability

HIGH
Advisory Identifier: GHSA-m99w-x7hq-7vfj
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CWE-834
Published
Advisory Summary

CVE-2026-64641 is a HIGH denial of service vulnerability (CWE-834: Excessive Iteration) affecting Next libraries in the npm ecosystem. The issue involves denial of service in app router using server actions. Remediation is available by upgrading affected packages to version 15.5.21, 16.2.11.

CVE-2026-64641 at a Glance

CVE Identifier CVE-2026-64641
GHSA Identifier GHSA-m99w-x7hq-7vfj
Severity HIGH
CVSS v3.1 Base Score N/A
CWE Classification CWE-834: Excessive Iteration
Affected Product Next
Package Ecosystem npm
Published Date
Last Updated

How to Fix CVE-2026-64641

To remediate this vulnerability, upgrade all affected Next dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

next fixed: 15.5.21 
npm install next@15.5.21
next fixed: 16.2.11 
npm install next@16.2.11
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

npm ls next

How to Check if You Are Affected

To determine whether your Node.js application is affected by CVE-2026-64641, inspect your project dependencies using npm:

npm ls next

Analyze the terminal output to locate any version of Next in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 15.5.21), your application is affected.

Note: The npm ls next command inspects dependencies declared in your package.json and lockfile; it does not perform automated runtime dynamic scanning.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-834: Excessive Iteration, where the product performs an iteration or loop without sufficiently limiting the number of times that the loop is executed. In Next, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

## Impact 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. ## Workarounds No workaround exists besides upgrading. Applications using Pages Router or not using Server Actions are not vulnerable.

CVE-2026-64641 Affected Next Versions

2 component(s)
Fixed Versions:
15.5.2116.2.11
Product / Package Ecosystem Affected Versions Fixed Version
next
npm/next
npm
≥ 13.0.0
< 15.5.21
15.5.21
next
npm/next
npm
≥ 16.0.0
< 16.2.11
16.2.11

References

GitHub Advisory / Wiki ADVISORY
https://github.com/vercel/next.js/security/advisories/GHSA-m99w-x7hq-7vfj
Next Source Repository REPOSITORY
https://github.com/vercel/next.js/pull/96013
Security Fix Commit FIX COMMIT
https://github.com/vercel/next.js/commit/019628571641dec57aaf349ba0c360e3964e6f12
Next Source Repository REPOSITORY
https://github.com/vercel/next.js
Next Release RELEASE
https://github.com/vercel/next.js/releases/tag/v15.5.21
Next Release RELEASE
https://github.com/vercel/next.js/releases/tag/v16.2.11

Frequently Asked Questions

What is CVE-2026-64641?
CVE-2026-64641 is a security vulnerability in Next involving Denial of Service in App Router using Server Actions under CWE-834: Excessive Iteration.
Which Next versions are affected?
Affected versions include releases prior to 15.5.21, 16.2.11 across affected packages: next.
What version fixes CVE-2026-64641?
Upgrading to 15.5.21, 16.2.11 (or the latest patched release for your respective branch) resolves the vulnerability.
Is next affected?
Yes, next is affected in releases prior to 15.5.21, 16.2.11. Upgrade your dependency to 15.5.21, 16.2.11 or later.
What CWE is associated with CVE-2026-64641?
CVE-2026-64641 is classified under CWE-834: Excessive Iteration (The product performs an iteration or loop without sufficiently limiting the number of times that the loop is executed.).
How can I check npm dependencies for CVE-2026-64641?
Run the dependency tree command: 'npm ls next'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-m99w-x7hq-7vfj",
  "modified" : "2026-07-22T22:59:01Z",
  "published" : "2026-07-22T22:59:01Z",
  "aliases" : [ "CVE-2026-64641" ],
  "summary" : "Next.js: Denial of Service in App Router using Server Actions",
  "details" : "## Impact\n\nCrafted 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.\n\n## Workarounds\n\nNo workaround exists besides upgrading. Applications using Pages Router or not using Server Actions are not vulnerable.",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "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"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "next"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "13.0.0"
      }, {
        "fixed" : "15.5.21"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "npm",
      "name" : "next"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "16.0.0"
      }, {
        "fixed" : "16.2.11"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/vercel/next.js/security/advisories/GHSA-m99w-x7hq-7vfj"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/vercel/next.js/pull/96013"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/vercel/next.js/commit/019628571641dec57aaf349ba0c360e3964e6f12"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/vercel/next.js"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/vercel/next.js/releases/tag/v15.5.21"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/vercel/next.js/releases/tag/v16.2.11"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-834" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-07-22T22:59:01Z",
    "nvd_published_at" : null
  }
}