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Microsoft CVE-2026-34401

| EUVD-2026-17666 MEDIUM
Improper Restriction of XML External Entity Reference (CWE-611)
2026-03-31 GitHub_M
6.5
CVSS 3.1
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CVSS VectorNVD

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N
Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
Required
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
None

Lifecycle Timeline

4
Patch available
Apr 16, 2026 - 05:29 EUVD
2.9.0.21
EUVD ID Assigned
Mar 31, 2026 - 21:31 euvd
EUVD-2026-17666
Analysis Generated
Mar 31, 2026 - 21:31 vuln.today
CVE Published
Mar 31, 2026 - 21:05 nvd
MEDIUM 6.5

DescriptionNVD

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.

AnalysisAI

XML Notepad versions prior to 2.9.0.21 allow remote attackers to leak local file contents or capture NTLM credentials via crafted XML files with malicious DTDs, exploiting disabled-by-default DTD processing that automatically resolves external entities. The vulnerability requires user interaction (opening a malicious XML file) but poses significant confidentiality risk on Windows systems where NTLM credential interception is feasible. …

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CVE-2026-34401 vulnerability details – vuln.today

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