CVE-2026-44708
XSS vulnerability in mistune (PyPI)
What is CVE-2026-44708 About?
The `mistune` math plugin renders user-supplied math content directly into HTML without any HTML escaping, even when `escape=True` is enabled for the parser. This creates a Cross-Site Scripting (XSS) vulnerability, allowing attackers to inject arbitrary HTML or JavaScript code into the rendered output. This is a severe bypass of an explicit security control, making exploitation easy and highly impactful.
Affected Software
Technical Details
The vulnerability lies in src/mistune/plugins/math.py, specifically in render_inline_math() and render_block_math() functions. These functions take raw user input (text) and concatenate it directly into the HTML output string without performing any HTML escaping. The critical issue is that they neither call escape(text) from mistune.util nor check the renderer._escape flag. While the escape=True flag correctly sanitizes input for other HTMLRenderer methods (e.g., paragraphs, headings), the math plugin operates as an independent render path that completely disregards this global setting. For example, $ <script>alert(document.cookie)</script> $ or $$ <img src=x onerror="alert(1)"> $$ will be rendered verbatim into the HTML, leading to direct script execution or attribute injection.
What is the Impact of CVE-2026-44708?
Successful exploitation may allow attackers to achieve Cross-Site Scripting (XSS). This enables them to exfiltrate session cookies and authentication tokens, mutate page content, inject phishing forms, redirect users, or perform authenticated actions on behalf of the victim. It can also lead to denial-of-service by crashing or freezing the user's browser page.
What is the Exploitability of CVE-2026-44708?
Exploitation of this XSS vulnerability is of low complexity. It requires no authentication and relies only on the ability for an attacker to provide content that will be rendered by the mistune parser with the math plugin enabled. Privilege requirements are negligible, as it affects client-side execution triggered by server-side rendering. The attack is inherently remote, as the malicious content is delivered and processed by a web application. The primary risk factor is any application that uses mistune with the math plugin to render untrusted user-supplied content, especially developers who believe escape=True provides full XSS protection. This bypass of an explicit security control significantly increases the likelihood of an attacker successfully injecting malicious code.
What are the Known Public Exploits?
| PoC Author | Link | Commentary |
|---|---|---|
| No known exploits | ||
What are the Available Fixes for CVE-2026-44708?
Available Upgrade Options
- No fixes available
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What are Similar Vulnerabilities to CVE-2026-44708?
Similar Vulnerabilities: CVE-2023-24838 , CVE-2023-2844 , CVE-2023-29402 , CVE-2023-33385 , CVE-2023-44487
