CVE-2026-27979: 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 th...

Description

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.

Metrics

CVSS 3.1

7.5/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS 4.0

6.9/10

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

EPSS Probability

0.48%

38.0th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-770

Affected Software

Vendor	Product	Versions
Vercel	Next.Js	>= 16.0.1, < 16.1.7

References

https://github.com/vercel/next.js/commit/c885d4825f800dd1e49ead37274dcd08cdd6f3f1Patch
https://github.com/vercel/next.js/releases/tag/v16.1.7Release Notes
https://github.com/vercel/next.js/security/advisories/GHSA-h27x-g6w4-24gqMitigation, Vendor Advisory

Timeline

Published: Mar 18, 2026
Last Modified: Jun 17, 2026
Status: Analyzed

Frequently Asked Questions

What is CVE-2026-27979?

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.

How severe is CVE-2026-27979?

CVE-2026-27979 has a CVSS score of 6.9/10 (MEDIUM severity). The EPSS model estimates a 0.48% probability of exploitation in the next 30 days.

How do I fix CVE-2026-27979?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.