CVE-2026-34401— XML Notepad: XML External Entity (XXE) Injection via Unsafe XmlTextReader in XML Diff and Schema Loading
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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: NVD (National Vulnerability Database)
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: NVD (National Vulnerability Database)
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N
Source: NVD (National Vulnerability Database)
Vulnerability Type
XML外部实体引用的不恰当限制(XXE)
Source: NVD (National Vulnerability Database)
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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- Release Xml Notepad 2.9.0.21 · microsoft/XmlNotepad · GitHubx_refsource_MISC
- https://nvd.nist.gov/vuln/detail/CVE-2026-34401
IV. Related Vulnerabilities
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Same weakness: CWE-611
- CVE-2026-41936
Vvveb < 1.0.8.2 XML External Entity Injection via Import - CVE-2026-40682
Apache OpenNLP: XXE via Dictionary Parsing in DictionaryEntr - CVE-2026-6501
ILM Informatique jOpenDocument 代码问题漏洞 - CVE-2025-14543
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Arbitrary File Read and Server Side Request Forgery via XML
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