Next-Mdx-Remote Vulnerability Learn more Tools for endpoint detection and response Taking advantage of ethical hacking tools A security warning A serious flaw in the next-mdx-remote library was discovered by HCSEC-2026-01, which enables attackers to run arbitrary code on servers that render untrusted MDX content This article explores mdx remote vulnerability. . The problem, identified as CVE-2026-0969, is fixed in 6.0.0 and impacts versions 4.3.0 through 5.0.0.

A well-liked open-source TypeScript library for React apps built with Next.js is called Next-mdx-remote. It enables developers to dynamically render MDX (Markdown with JSX) on the server or client by pulling it from databases, APIs, or user input. The Attack's Mechanism MDX is ideal for blogs, documents, and user-generated content because it combines the simplicity of Markdown with React components. The serialize and compileMDX functions in the library are the source of the issue.

These lacked proper sanitization for JavaScript expressions in untrusted MDX. Aspect Information CVE ID CVE-2026-0969 Affected next-mdx-remote 4.3.0 to 5.0.0 CVSS Score Critical (estimated 9.8/10) Impact RCE on SSR with untrusted MDX Attackers could sneak in malicious code such as eval(), Function(), or require() hidden in curly braces {}. When the server processes this during server-side rendering (SSR), it executes the code with full server privileges.

This leads to remote code execution (RCE), potentially letting hackers steal data, install malware, or take over the server. Discover more Data breach monitoring Secure file sharing Endpoint security solutions For example, an attacker submits MDX like: {require(‘child_process’).execSync(‘rm -rf /’)}. If JavaScript expressions are enabled (the default), the server runs them blindly.

Breaking changes are included in version 6.0.0: By default, JavaScript expressions are now blocked (blockJS: true). A new blockDangerousJS: true option (default on) filters risky globals like process, eval, and require when it is enabled (blockJS: false). If you handle untrusted MDX on servers, you should update to next-mdx-remote 6.0.0 right away.

Code auditing for serialize or compile MDX calls. Never render MDX supplied by the user without first sanitizing it. For added security, use libraries such as remark-rehype. To identify deviations from the defaults, test in staging.

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