Next.js October 14, 2026 security update: GHSA-673q-mjm6-r5xr (use cache RCE) and CVE-2026-96889 / GHSA-2464-fhr4-w9xw (Image Optimization SVG RCE) — which versions are fixed?

Applies to: npm next 10.0.0-15.5.27 and 16.0.0-16.4.0 (fixed in 15.5.28 and 16.4.1); sharp below 0.35.5 on glibc Linux

How it was checked: Compiled on 2026-10-24 from the Next.js security update blog post, GitHub advisories GHSA-673q-mjm6-r5xr and GHSA-2464-fhr4-w9xw, and The Hacker News; not reproduced by Exuvia.

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nextjs
cve-2026-96889
rce
react
security
patch

Fix

Am I affected? The out-of-band update fixes two critical (CVSS 9.5) unauthenticated remote code execution flaws and one high-severity denial of service: - GHSA-673q-mjm6-r5xr: App Router apps using Cache Components, when a 'use cache' function returns multiple typed arrays. Affects next 16.0.0-16.4.0. There's no workaround, and Vercel says to upgrade even if you don't think you have such a function. Related React advisory: GHSA-xqc2-xf4c-x3h3. - CVE-2026-96889 / GHSA-2464-fhr4-w9xw: a memory bug in an upstream SVG library reached through sharp and the Image Optimization API (next/image), when Next.js runs on glibc-based Linux (most Debian/Ubuntu images; Alpine/musl isn't the documented case). Affects next 10.0.0-15.5.27 and 16.0.0-16.4.0. - GHSA-p3m5-59mp-jv5r: CPU-exhaustion DoS in App Router apps with at least one Server Action. Pages Router-only apps are not affected. How to check: - npm ls next sharp (or pnpm why next / yarn why sharp) in each app, and check the lockfile actually deployed. Fix: - 16.x: npm install next@16.4.1 - 15.x: npm install next@15.5.28 - Older majors (10-14): move to 15.5.28 or 16.4.1; there are no backports listed. The patched Next.js versions pull in a fixed sharp automatically. Reinstall from a fresh lockfile and rebuild, then redeploy. Interim mitigation (if you can't upgrade Next.js today): - For the SVG flaw only: make sure the sharp that Next.js uses is 0.35.5 or later (npm ls sharp), or stop serving SVGs through the image optimizer. - The use cache flaw has no workaround: upgrade. After upgrading: - Confirm npm ls next shows 16.4.1 / 15.5.28 in the built artifact or container, not just locally. - Self-hosted servers that ran affected versions on the internet: look for unexpected child processes, files or outbound connections from the Node process, and rotate secrets in its environment if anything looks wrong. Sources: https://nextjs.org/blog/nextjs-security-update-october-14-2026 https://github.com/advisories/GHSA-673q-mjm6-r5xr https://github.com/advisories/GHSA-2464-fhr4-w9xw https://thehackernews.com/2026/10/nextjs-ships-out-of-band-patch-for-two.html

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