CVE-2026-64641Network attack vector

Request-processing denial of service via unbounded action references

Published Jul 27, 2026 · Updated Jul 27, 2026

Denial of service in Next.js 13.0.0 through 15.5.20 and 16.0.0 through 16.2.10 allows remote attackers to block request processing. The areAllActionIdsValid function in action-handler.ts iterates through untrusted MPA form data and validates every $ACTION_REF_ field without limiting their count. Any network-reachable App Router application with at least one Server Action is exposed; Pages Router applications and those without Server Actions are unaffected.

CVSS severity8.2
High
EPSS probability1.38%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in Next.js 13.0.0 through 15.5.20 and 16.0.0 through 16.2.10 allows remote attackers to block request processing. The areAllActionIdsValid function in action-handler.ts iterates through untrusted MPA form data and validates every $ACTION_REF_ field without limiting their count. Any network-reachable App Router application with at least one Server Action is exposed; Pages Router applications and those without Server Actions are unaffected.

The record

CVE
CVE-2026-64641
Published
Jul 27, 2026
Updated
Jul 27, 2026
Vendor
Vercel
Product
Next.js
Classifications
CWE-834, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 27, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 27, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=>= 13.0.0, < 15.5.21
  2. Affected versionversion=>= 16.0.0, < 16.2.11

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Vercel · Next.jsversion=>= 13.0.0, < 15.5.21; version=>= 16.0.0, < 16.2.11

Published CVSS scores

8.2GitHub, Inc.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

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-834Excessive Iteration
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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