Executive Summary

CVE-2026-0969 is an arbitrary code execution vulnerability in the next-mdx-remote library, specifically affecting versions from 4.3.0 up to 5.0.0.

The issue arises from the serialize function used to compile MDX content, which lacks sufficient sanitization when processing untrusted MDX input containing JavaScript expressions.

This flaw can lead to remote code execution (RCE) on the server side because dangerous JavaScript operations such as eval, Function constructor, process, require, and other global objects are not properly filtered.

next-mdx-remote is a TypeScript library that enables dynamic rendering of MDX content on both client and server environments.

Useful 0 Not Useful 0

Impact Analysis

If you use next-mdx-remote versions 4.3.0 to 5.0.0 in server environments that accept untrusted MDX content with enabled JavaScript expressions, an attacker can exploit this vulnerability to execute arbitrary code on your server.

This can lead to full compromise of the server, including unauthorized access, data theft, or disruption of services.

To mitigate this risk, upgrading to version 6.0.0 or later is recommended, where JavaScript expressions are disabled by default and additional protections against dangerous JavaScript operations are enabled.

Useful 0 Not Useful 0

Compliance Impact

I don't know

Useful 0 Not Useful 0

Detection Guidance

[{'type': 'paragraph', 'content': 'Detection of this vulnerability involves identifying usage of the next-mdx-remote library versions from 4.3.0 up to 5.0.0 in your environment, especially where untrusted MDX content is processed with JavaScript expressions enabled.'}, {'type': 'paragraph', 'content': 'You can check the installed version of next-mdx-remote in your project by running the following command in your project directory:'}, {'type': 'list_item', 'content': 'npm list next-mdx-remote'}, {'type': 'paragraph', 'content': 'Additionally, to detect if your code uses the vulnerable serialize function with JavaScript expressions enabled, you can search your codebase for usage patterns like:'}, {'type': 'list_item', 'content': "grep -r 'serialize(' ./"}, {'type': 'list_item', 'content': 'and check if the option `blockJS` is set to false or not set at all.'}, {'type': 'paragraph', 'content': 'Since this vulnerability is related to server-side rendering of untrusted MDX content, monitoring logs for suspicious execution or unexpected code execution patterns may also help in detection.'}] [1]

Useful 0 Not Useful 0

Mitigation Strategies

To mitigate this vulnerability, you should upgrade the next-mdx-remote library to version 6.0.0 or later, where JavaScript expressions are disabled by default via the `blockJS: true` option.

If you need to enable JavaScript expressions (`blockJS: false`), ensure that the `blockDangerousJS: true` option is also enabled to provide best-effort protection against dangerous JavaScript operations that could lead to arbitrary code execution.

Additionally, avoid processing untrusted MDX content with JavaScript expressions enabled, or sanitize and validate all MDX input before rendering.

Useful 0 Not Useful 0