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Description

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.

PUBLISHED Reserved 2026-03-27 | Published 2026-03-31 | Updated 2026-04-01 | Assigner GitHub_M




MEDIUM: 6.5CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N

Problem types

CWE-611: Improper Restriction of XML External Entity Reference

Product status

< 2.9.0.21
affected

References

github.com/...otepad/security/advisories/GHSA-5j32-486h-42ch exploit

github.com/...otepad/security/advisories/GHSA-5j32-486h-42ch

github.com/...ommit/3665603d61ba10b7827a3724e854748cb780140c

github.com/...ommit/c03ab2311ac6960452eb1ab49098768f851dcc53

github.com/microsoft/XmlNotepad/releases/tag/2.9.0.21

cve.org (CVE-2026-34401)

nvd.nist.gov (CVE-2026-34401)

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