Next.js Patches Critical AVIF and Windows Flaws Enabling Unauthenticated RCE
Vercel patches two critical Next.js unauthenticated RCE flaws: a libheif AVIF heap overflow (CVSS 9.5) and a Windows path traversal (CVE-2026-75604).
Vercel patched two critical Next.js flaws enabling unauthenticated remote code execution: a heap buffer overflow in libheif's AVIF image scaling (GHSA-2xp9-vwfh-vxw4, CVSS v4 9.5) and a Windows path traversal (CVE-2026-75604, CVSS 9.0). The AVIF flaw affects only sites explicitly enabling AVIF optimization and overwrites roughly 16,384 bytes past the buffer; the path traversal affects Windows-hosted Next.js deployments on versions 13.4-15.5.23 and 16.0-16.3.2. Fixes shipped in Next.js 15.5.24 and 16.3.3 on August 25, 2026, with the AVIF researchers releasing a Python PoC demonstrating RCE on multiple applications. No exploitation had been reported as of August 27, 2026.
- libheif heap overflow writes 16-bit samples into an 8-bit-sized buffer, ~16KB out-of-bounds write
- Windows path traversal affects Pages Router and App Router without Cache Components on Windows filesystems
- Patched in Next.js 15.5.24 and 16.3.3; Vercel-hosted apps require no action
- AVIF optimization disabled in patched releases pending upstream libheif v1.23.2 fix
- CVEs
- CVE-2026-75604
Vulnerabilities mentioned
All| CVE | Vulnerability | CVSS | EPSS | Signals | Published |
|---|---|---|---|---|---|
| CVE-2026-75604 | Unauthenticated RCE in Next.js on Windows-hosted servers | 9.0 | 2% | PoC |
From the original article
3 min read at thehackernews.com
Vercel has released security patches for two critical-severity vulnerabilities in the Next. js web framework, both of which allow unauthenticated remote code execution, one exploitable via specially crafted AVIF image files and the other through a path traversal flaw affecting servers that use a Windows filesystem. The Windows path traversal, tracked as CVE-2026-75604 (CVSS score: 9.
By @TheHackersNews · thehackernews.com
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