PT-2026-29357 · Microsoft · Xmlnotepad

Published 2026-03-31 · Updated 2026-03-31 · CVE-2026-34401

Mitre

CVSS v3.1

6.5

Medium

AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N

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.

Fix

XXE

Weakness Enumeration

CWE-611

Related Identifiers

CVE-2026-34401

Affected Products

Xmlnotepad

References · 5

• https://nvd.nist.gov/vuln/detail/CVE-2026-34401 · Security Note
• https://github.com/microsoft/XmlNotepad/security/advisories/GHSA-5j32-486h-42ch · Note
• https://github.com/microsoft/XmlNotepad/commit/c03ab2311ac6960452eb1ab49098768f851dcc53 · Note
• https://github.com/microsoft/XmlNotepad/commit/3665603d61ba10b7827a3724e854748cb780140c · Note
• https://github.com/microsoft/XmlNotepad/releases/tag/2.9.0.21 · Note