XXE in Microsoft Xmlnotepad
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 re…
Vulnerability class: XXE (XML External Entity)
EPSS: 0.003 (52.2th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 6.5 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N.
Affected products
- Microsoft Xmlnotepad — versions < 2.9.0.21
Weakness classification (CWE)
References
- https://github.com/microsoft/XmlNotepad/security/advisories/GHSA-5j32-486h-42ch (x_refsource_CONFIRM)
- https://github.com/microsoft/XmlNotepad/commit/3665603d61ba10b7827a3724e854748cb780140c (x_refsource_MISC)
- https://github.com/microsoft/XmlNotepad/commit/c03ab2311ac6960452eb1ab49098768f851dcc53 (x_refsource_MISC)
- https://github.com/microsoft/XmlNotepad/releases/tag/2.9.0.21 (x_refsource_MISC)
Frequently asked questions
- What is CVE-2026-34401?
- CVE-2026-34401 is a medium-severity vulnerability in Microsoft Xmlnotepad, classified under Improper Restriction of XML External Entity Reference (XXE). CVSS score: 6.5/10. Published 2026-03-31.
- How severe is CVE-2026-34401?
- Medium severity. CVSS v3 base score is 6.5 out of 10.