Next.js Critical AVIF Parsing and Windows Path Traversal Vulnerabilities

Technical Analysis

The Windows-specific vulnerability, tracked as CVE-2026-75604, is a path traversal issue that allows attackers to escape intended directory boundaries on servers running Next.js on Windows filesystems, potentially leading to arbitrary file read/write and unauthenticated RCE. The second flaw involves malicious AVIF image file parsing within Next.js's image optimization pipeline, allowing crafted image inputs to trigger code execution during server-side processing. Both vulnerabilities require no authentication, making them highly exploitable at scale against internet-facing Next.js applications. Given that many AI agent frameworks, RAG pipelines, and LLM-powered web applications use Next.js as a front-end or API layer to serve agent interfaces, successful exploitation could grant attackers direct access to hosts running agent orchestration code, exposing API keys, model credentials, and internal tool-calling infrastructure.

Affected Systems

Next.js web framework servers using the built-in image optimization feature for AVIF processing; Next.js deployments running on Windows filesystems susceptible to path traversal via CVE-2026-75604

Indicators of Compromise

• No specific IOCs published at time of disclosure; monitor Next.js security advisories for exploit signatures

Remediation Steps

1. 1

   Apply Vendor Patch

   Update to the latest patched version of Next.js as released by Vercel to remediate both the AVIF parsing RCE and the Windows path traversal vulnerability (CVE-2026-75604).

2. 2

   Restrict Image Optimization Inputs

   Where immediate patching is not possible, disable or restrict the built-in image optimization API to trusted sources only, and validate/sanitize uploaded image formats.

3. 3

   Audit Windows-Hosted Deployments

   Review file system permissions and path handling on any Next.js instances running on Windows to reduce traversal exposure until patched.

4. 4

   Monitor for Exploitation

   Enable logging and monitoring on Next.js application servers for anomalous file access patterns or unexpected image processing errors indicative of exploitation attempts.

5. 5

   Rotate Exposed Credentials

   If compromise is suspected, rotate API keys, service credentials, and secrets accessible from the affected host, particularly those used by AI agent or LLM tooling integrations.