Vulnerability Details CVE-2026-34401
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.
Exploit prediction scoring system (EPSS) score
EPSS Score 0.002
EPSS Ranking 47.0%
CVSS Severity
CVSS v3 Score 6.5
References
- https://github.com/microsoft/XmlNotepad/commit/3665603d61ba10b7827a3724e854748cb780140c
- https://github.com/microsoft/XmlNotepad/commit/c03ab2311ac6960452eb1ab49098768f851dcc53
- https://github.com/microsoft/XmlNotepad/releases/tag/2.9.0.21
- https://github.com/microsoft/XmlNotepad/security/advisories/GHSA-5j32-486h-42ch
- https://github.com/microsoft/XmlNotepad/security/advisories/GHSA-5j32-486h-42ch
Products affected by CVE-2026-34401
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cpe:2.3:a:microsoft:xml_notepad:*