CVE-2026-27979: Next.js: Unbounded postponed resume buffering can lead to DoS
Summary A request containing the next-resume: 1 header (corresponding with a PPR resume request) would buffer request bodies without consistently enforcing maxPostponedStateSize in certain setups. The previous mitigation protected minimal-mode deployments, but equivalent non-minimal deployments remained vulnerable to the same unbounded postponed resume-body buffering behavior.
Impact In applications using the App Router with Partial Prerendering capability enabled (via experimental.ppr or cacheComponents), an attacker could send oversized next-resume POST payloads that were buffered without consistent size enforcement in non-minimal deployments, causing excessive memory usage and potential denial of service.
Patches Fixed by enforcing size limits across all postponed-body buffering paths and erroring when limits are exceeded.
Workarounds If upgrade is not immediately possible: - Block requests containing the next-resume header, as this is never valid to be sent from an untrusted client.
Other sources
Next.js is a React framework for building full-stack web applications. Starting in version 16.0.1 and prior to version 16.1.7, a request containing the next-resume: 1 header (corresponding with a PPR resume request) would buffer request bodies without consistently enforcing maxPostponedStateSize in certain setups. The previous mitigation protected minimal-mode deployments, but equivalent non-minimal deployments remained vulnerable to the same unbounded postponed resume-body buffering behavior. In applications using the App Router with Partial Prerendering capability enabled (via experimental.ppr or cacheComponents), an attacker could send oversized next-resume POST payloads that were buffered without consistent size enforcement in non-minimal deployments, causing excessive memory usage and potential denial of service. This is fixed in version 16.1.7 by enforcing size limits across all postponed-body buffering paths and erroring when limits are exceeded. If upgrading is not immediately possible, block requests containing the next-resume header, as this is never valid to be sent from an untrusted client.
— MITRE
Affected Software
Remediation
Event History
Frequently Asked Questions
What is the severity of CVE-2026-27979?
The severity of CVE-2026-27979 is considered to be high due to potential impacts on request body processing.
How do I fix CVE-2026-27979?
To fix CVE-2026-27979, upgrade to Next.js version 16.1.7 or later.
What types of software are affected by CVE-2026-27979?
CVE-2026-27979 affects specific versions of the Next.js package on npm.
What does CVE-2026-27979 impact in Next.js?
CVE-2026-27979 impacts the handling of PPR resume requests with the `next-resume: 1` header.
Is there a specific configuration to be aware of for CVE-2026-27979?
Yes, CVE-2026-27979 indicates that certain deployments may buffer request bodies without properly enforcing `maxPostponedStateSize`.