---
id: CVE-2026-34401
title: >-
  XML Notepad is a Windows program that provides a simple intuitive User
  Interface for browsing and editing XML documents
summary: >-
  XML Notepad is a Windows program that provides a simple intuitive User
  Interface for browsing and editing XML documents. Prior to version 2.9.0.21,
  XML Notepad does not disable DTD processing by default which means external
  entities are …
severity: medium
cvss: 6.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N'
cwe:
  - CWE-611
vendor: microsoft
product: xml_notepad
affected:
  - xml_notepad < 2.9.0.21
patched:
  - xml_notepad 2.9.0.21
published: '2026-03-31'
updated: '2026-07-24'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-34401'
references:
  - url: >-
      https://github.com/microsoft/XmlNotepad/commit/3665603d61ba10b7827a3724e854748cb780140c
    label: security-advisories@github.com
  - url: >-
      https://github.com/microsoft/XmlNotepad/commit/c03ab2311ac6960452eb1ab49098768f851dcc53
    label: security-advisories@github.com
  - url: 'https://github.com/microsoft/XmlNotepad/releases/tag/2.9.0.21'
    label: security-advisories@github.com
  - url: >-
      https://github.com/microsoft/XmlNotepad/security/advisories/GHSA-5j32-486h-42ch
    label: security-advisories@github.com
  - url: >-
      https://github.com/microsoft/XmlNotepad/security/advisories/GHSA-5j32-486h-42ch
    label: 134c704f-9b21-4f2e-91b3-4a467353bcc0
tags:
  - nvd
epss: 0.00986
epssPercentile: 0.60912
ingestedAt: '2026-07-25T21:03:57.827Z'
---

## Overview

XML Notepad is a Windows program that provides a simple intuitive User Interface for browsing and editing XML documents. Prior to version 2.9.0.21, XML Notepad does not disable DTD processing by default which means external entities are resolved automatically. There is a well known attack related to malicious DTD files where an attacker to craft a malicious XML file that loads a DTD that causes XML Notepad to make outbound HTTP/SMB requests, potentially leaking local file contents or capturing the victim's NTLM credentials. This issue has been patched in version 2.9.0.21.

## Affected

- `xml_notepad < 2.9.0.21`

## Remediation

Upgrade past the affected range:

- `xml_notepad 2.9.0.21`