Description of CVE-2025-65108
For those who don't know, Markdown is a simple markup language used to format text with easy-to-remember and easy-to-type characters. It is designed to be:
Easy to read in plain text.
Easy to write.
Easy to convert to HTML, PDF, and other formats.
To understand better, I'll show you some special characters that are easy to use in Markdown, such as:
| You type | Markdown will display as |
# Title | Large Title |
**bold** | bold |
*italic* | italic |
- list | list |
code | code |
Because of its convenience, Markdown is widely used by developers, document writers, and bloggers, which also makes it a potential target for vulnerabilities that attackers want to exploit. In November 2025, cybersecurity experts identified a new vulnerability labeled CVE-2025-65108, rated CVSS 10.0 – absolute danger level, revealing that just a piece of front-matter in Markdown can open the door to Remote Code Execution.
This vulnerability is not just a software bug; it highlights the thin line between "text formatting" and "malicious code execution." If you are using tools to convert Markdown to PDF in your system, this could be a ticking time bomb silently counting down...
Scope of Impact
Any environment that converts Markdown to PDF using the md-to-pdf library (all versions before 5.2.5) is at risk of exploitation.
The impact scope of CVE-2025-65108 is not limited to web applications but extends to the entire ecosystem, including:
Dev tools,
Automation pipelines,
Cloud services,
Internal infrastructure.
Wherever untrusted Markdown is converted to PDF, this vulnerability can become a dangerous RCE vector.
Severity Assessment
CVE-2025-65108 is rated as CRITICAL with the following scores:
Analysis and Exploitation of the Vulnerability
First, as mentioned, the attacker will prepare an executable payload, and it can only occur when one of the following conditions is met:
A plugin/extension in the md-to-pdf pipeline is enabled, and that plugin actively executes JavaScript code blocks in the Node context (for example, plugins like remark-exec / rehype-run or a custom plugin that calls eval, vm.runInThisContext, new Function, or require on the code block content).
md-to-pdf (or a dependency) contains a vulnerability that allows injecting/executing Node code from the markdown content (for example, using a template engine with unsafe interpolation like _.template or handlebars without sanitizing).
The user runs md-to-pdf with custom configurations that allow running hooks or scripts taken from the Markdown content.
After preparing a payload as mentioned, the attacker will introduce this file into the system in several ways: upload, commit PR, send an email, or pass it into an API. Here, when the user activates md-to-pdf to convert the file, the parser reads the front-matter and evaluates.
As you can see, ---javascript and ---RCE here are not standard front-matter (front-matter is usually ---\nkey: value\n---) and are being exploited to execute the attack. The function ((require("child_process")).execSync("calc.exe")) will be called - this is a JavaScript command running in the Node.js environment.
require("child_process") gets the child_process module.
.execSync("calc.exe") runs the system command calc.exe synchronously - on Windows, this will open the Calculator. On Linux/Mac, this command will return an error if calc.exe does not exist.
The goal of the payload: if this JS code is executed in the Node.js context (not in the browser), it will call the subsystem and execute the command - which means local RCE (remote code execution). A dangerous point here is that if the server runs with high privileges (root/Administrator), the consequences are more severe (full system access).
Once an attacker has executed code on the system (e.g., RCE through the payload as you analyzed earlier), the post-exploitation steps usually aim to:
Recommendation
Update to md-to-pdf version ≥ 5.2.5
Prevent untrusted Markdown processing
Use only trusted Markdown sources
Do not download or open Markdown files (.md) from unclear sources.
Do not copy/paste strange Markdown content into PDF conversion systems.
Avoid using Markdown templates shared over the Internet if the source is not verified.
Check front-matter before opening or uploading Markdown
If you see sections like:
or content with unusual keywords such as:
child_process
execSync
require(
process.mainModule
Stop processing immediately, as this could be a payload designed to exploit an RCE vulnerability.
Do not share or upload sensitive Markdown to untrusted online services
Summary
The vulnerability CVE-2025-65108 reveals an unsettling truth: even seemingly harmless tools like Markdown to PDF converters can become the starting point for a full-scale attack. Injecting JavaScript through front-matter and executing code within md-to-pdf has turned a simple document processing task into a serious RCE point, rated CVSS 10.0 – the highest possible level.
The impact spreads widely, from web applications to CI/CD pipelines, from cloud services to internal systems. This creates an urgent need to update versions, review the entire Markdown processing workflow, and apply safe isolation measures for document conversion tasks.
CVE-2025-65108 is not just a vulnerability; it's a reminder that the line between "data" and "executable code" is always fragile. A single misconfiguration or an overlooked feature is enough for an attacker to turn a Markdown document into a weapon. Acting early is crucial to limit risks and protect systems from unforeseen consequences.
References
Critical Markdown to PDF Flaw (CVE-2025-65108, CVSS 10.0) Allows RCE via JS Injection in Markdown Front-Matter
NVD - CVE-2025-65108
md-to-pdf vulnerable to arbitrary JavaScript code execution when parsing front matter · CVE-2025-65108 · GitHub Advisory Database · GitHub
