CVE-2026-34401— XML Notepad: XML External Entity (XXE) Injection via Unsafe XmlTextReader in XML Diff and Schema Loading
Possible ATT&CK Techniques 3AI
T1005 · Data from Local System T1041 · Exfiltration Over C2 Channel T1059 · Command and Scripting InterpreterGet alerts for future matching vulnerabilitiesLog in to subscribe
I. Basic Information for CVE-2026-34401
Vulnerability Information
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Vulnerability Title
XML Notepad: XML External Entity (XXE) Injection via Unsafe XmlTextReader in XML Diff and Schema Loading
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
XML外部实体引用的不恰当限制(XXE)
Source: CVE Program / CVE List V5
Vulnerability Title
XmlNotepad 代码问题漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
XmlNotepad是Microsoft开源的一个XML文档浏览与编辑工具。 XmlNotepad 2.9.0.21之前版本存在代码问题漏洞，该漏洞源于默认未禁用DTD处理，可能导致解析恶意XML文件时泄露本地文件内容或凭据。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)
Affected Products
| Vendor | Product | Affected Versions | CPE | Subscribe |
|---|---|---|---|---|
| microsoft | XmlNotepad | < 2.9.0.21 | - |
II. Public POCs for CVE-2026-34401
| # | POC Description | Source Link | Shenlong Link |
|---|
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Patches & Fixes for CVE-2026-34401 (2)
Vendor Advisories for CVE-2026-34401 (1)
Vendor Pages for CVE-2026-34401 (1)
IV. Related Vulnerabilities
Same vendor: microsoft
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Microsoft Edge (Chromium-based) Remote Code Execution Vulner - CVE-2026-73299
Prompty: Server-Side Template Injection to Remote Code Execu - CVE-2026-73298
Microsoft Container Migration Solution Accelerator: Authenti
Same weakness: CWE-611
- CVE-2026-69101
Datavane TIS v5.0.0 XXE Injection via doEditWorkflow Endpoin - CVE-2026-18715
IBM i is Affected By Multiple Vulnerabilities in WebSphere A - CVE-2026-15803
Eclipse RDF4J 输入验证错误漏洞 - CVE-2026-16999
XXE in Ministry of Justice's UYAP Document Editor - CVE-2026-73235
FreeCAD: XXE file read and SSRF via external entity injectio
V. Comments for CVE-2026-34401
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