Next.js August 2026 patches two critical RCE flaws; Vercel-hosted apps already protected

Two critical flaws patched in Next.js

Vercel has disclosed that Next.js's August 2026 Security Release addresses two vulnerabilities rated critical, each capable of letting an attacker run code on a vulnerable server without presenting any credentials. The announcement, published on the Vercel blog, also carries reassurance for the company's customers: deployments on the Vercel platform are already shielded, and customers need do nothing — no upgrades, configuration changes or redeploys. Self-hosted Next.js applications are a different matter and must move to patched releases.

A crafted AVIF image leads to code execution

The first vulnerability, tracked as GHSA-2xp9-vwfh-vxw4, has its roots in libheif, an upstream library in Next.js's image-processing stack. According to Vercel, a maliciously constructed AVIF image fed through the Image Optimization feature can result in remote code execution, with no authentication required from the attacker. The flaw was responsibly disclosed by a team Vercel identifies as Hacktron.

Because the defect lives in a dependency rather than in Next.js code, the current fix is deliberately blunt: patched builds of Next.js stop resizing or optimizing AVIF images entirely. AVIF files are delivered to visitors unchanged, and Vercel says optimization will return only once a corrected version of libheif is available.

A second flaw targets Windows-hosted servers

The second issue, CVE-2026-75604 (also published as GHSA-p293-qw3h-jr36), enables unauthenticated remote code execution on Next.js servers running on a Windows filesystem. According to Vercel, it affects applications built on either the Pages Router or the App Router, with one exception: apps using Cache Components are not exposed. Researchers evolutionstorm and B0RI are credited with the disclosure. There is no workaround for this one — Vercel's guidance is that affected Windows deployments upgrade immediately.

How Vercel insulated its platform

Once the AVIF issue was identified, Vercel switched off AVIF optimization across its managed Image Optimization service. Incoming AVIF files are handed through untouched rather than routed into the vulnerable processing path. The Windows flaw does not reach Vercel's infrastructure at all, since the company's Next.js runtime runs on Linux.

What self-hosters should do

For teams operating their own Next.js servers, the guidance is to upgrade to the appropriate patched release. Vercel notes that patched versions exist for applications on Next.js 15.x or earlier as well as for those on the 16.x line. Operators should expect AVIF optimization to stay disabled until libheif itself is fixed, and anyone running Next.js on Windows should treat the upgrade as urgent given the absence of any interim mitigation.

Why it matters

Both vulnerabilities are unauthenticated and remotely exploitable — the most severe class of web application flaw — and one of them sits in an image pipeline that many deployments expose to arbitrary user uploads. The incident also illustrates a widening gap in how security releases land: platform-managed deployments were protected before the disclosure even became public, while self-hosters shoulder the full burden of patching. If you run Next.js on your own Windows infrastructure, or process user-supplied AVIF images anywhere in your stack, this release is an immediate priority rather than routine maintenance.