{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-34401", "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa", "state": "PUBLISHED", "assignerShortName": "GitHub_M", "dateReserved": "2026-03-27T13:45:29.620Z", "datePublished": "2026-03-31T21:05:50.647Z", "dateUpdated": "2026-04-01T15:53:18.538Z"}, "containers": {"cna": {"title": "XML Notepad: XML External Entity (XXE) Injection via Unsafe XmlTextReader in XML Diff and Schema Loading", "problemTypes": [{"descriptions": [{"cweId": "CWE-611", "lang": "en", "description": "CWE-611: Improper Restriction of XML External Entity Reference", "type": "CWE"}]}], "metrics": [{"cvssV3_1": {"attackComplexity": "LOW", "attackVector": "NETWORK", "availabilityImpact": "NONE", "baseScore": 6.5, "baseSeverity": "MEDIUM", "confidentialityImpact": "HIGH", "integrityImpact": "NONE", "privilegesRequired": "NONE", "scope": "UNCHANGED", "userInteraction": "REQUIRED", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N", "version": "3.1"}}], "references": [{"name": "https://github.com/microsoft/XmlNotepad/security/advisories/GHSA-5j32-486h-42ch", "tags": ["x_refsource_CONFIRM"], "url": "https://github.com/microsoft/XmlNotepad/security/advisories/GHSA-5j32-486h-42ch"}, {"name": "https://github.com/microsoft/XmlNotepad/commit/3665603d61ba10b7827a3724e854748cb780140c", "tags": ["x_refsource_MISC"], "url": "https://github.com/microsoft/XmlNotepad/commit/3665603d61ba10b7827a3724e854748cb780140c"}, {"name": "https://github.com/microsoft/XmlNotepad/commit/c03ab2311ac6960452eb1ab49098768f851dcc53", "tags": ["x_refsource_MISC"], "url": "https://github.com/microsoft/XmlNotepad/commit/c03ab2311ac6960452eb1ab49098768f851dcc53"}, {"name": "https://github.com/microsoft/XmlNotepad/releases/tag/2.9.0.21", "tags": ["x_refsource_MISC"], "url": "https://github.com/microsoft/XmlNotepad/releases/tag/2.9.0.21"}], "affected": [{"vendor": "microsoft", "product": "XmlNotepad", "versions": [{"version": "< 2.9.0.21", "status": "affected"}]}], "providerMetadata": {"orgId": "a0819718-46f1-4df5-94e2-005712e83aaa", "shortName": "GitHub_M", "dateUpdated": "2026-03-31T21:05:50.647Z"}, "descriptions": [{"lang": "en", "value": "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": {"advisory": "GHSA-5j32-486h-42ch", "discovery": "UNKNOWN"}}, "adp": [{"references": [{"url": "https://github.com/microsoft/XmlNotepad/security/advisories/GHSA-5j32-486h-42ch", "tags": ["exploit"]}], "metrics": [{"other": {"type": "ssvc", "content": {"timestamp": "2026-04-01T15:45:24.184266Z", "id": "CVE-2026-34401", "options": [{"Exploitation": "poc"}, {"Automatable": "no"}, {"Technical Impact": "partial"}], "role": "CISA Coordinator", "version": "2.0.3"}}}], "title": "CISA ADP Vulnrichment", "providerMetadata": {"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-04-01T15:53:18.538Z"}}]}}

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{"configurations": [{"nodes": [{"cpeMatch": [{"criteria": "cpe:2.3:a:microsoft:xml_notepad:*:*:*:*:*:windows:*:*", "matchCriteriaId": "F08C7164-A566-4527-8764-F9BC54E164F1", "versionEndExcluding": "2.9.0.21", "vulnerable": true}], "negate": false, "operator": "OR"}]}], "cveTags": [], "descriptions": [{"lang": "en", "value": "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."}], "id": "CVE-2026-34401", "lastModified": "2026-04-13T15:19:47.710", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "NETWORK", "availabilityImpact": "NONE", "baseScore": 6.5, "baseSeverity": "MEDIUM", "confidentialityImpact": "HIGH", "integrityImpact": "NONE", "privilegesRequired": "NONE", "scope": "UNCHANGED", "userInteraction": "REQUIRED", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N", "version": "3.1"}, "exploitabilityScore": 2.8, "impactScore": 3.6, "source": "security-advisories@github.com", "type": "Secondary"}]}, "published": "2026-03-31T22:16:18.490", "references": [{"source": "security-advisories@github.com", "tags": ["Patch"], "url": "https://github.com/microsoft/XmlNotepad/commit/3665603d61ba10b7827a3724e854748cb780140c"}, {"source": "security-advisories@github.com", "tags": ["Patch"], "url": "https://github.com/microsoft/XmlNotepad/commit/c03ab2311ac6960452eb1ab49098768f851dcc53"}, {"source": "security-advisories@github.com", "tags": ["Product", "Release Notes"], "url": "https://github.com/microsoft/XmlNotepad/releases/tag/2.9.0.21"}, {"source": "security-advisories@github.com", "tags": ["Mitigation", "Vendor Advisory"], "url": "https://github.com/microsoft/XmlNotepad/security/advisories/GHSA-5j32-486h-42ch"}, {"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "tags": ["Mitigation", "Vendor Advisory"], "url": "https://github.com/microsoft/XmlNotepad/security/advisories/GHSA-5j32-486h-42ch"}], "sourceIdentifier": "security-advisories@github.com", "vulnStatus": "Analyzed", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-611"}], "source": "security-advisories@github.com", "type": "Secondary"}]}

{}

{"affected": [{"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "generic", "value": "[0,2.9.0.21)"}}], "enrichment": {"confidence": 100.0, "confidence_source": "cna", "scores": [{"score": 100.0, "source": "cna"}]}, "original": {"product": "XmlNotepad", "source": "cna", "vendor": "microsoft"}, "product": "xmlnotepad", "vendor": "microsoft"}], "analysis": {"en": {"generated_at": "2026-04-13T16:32:45.711615+00:00", "value": {"mitigation_remediation": ["Upgrade XML Notepad to version 2.9.0.21 or later.", "If upgrading cannot be performed immediately, restrict XML Notepad's outbound network access by configuring firewall rules or disabling internet and SMB shares."], "summary": {"action": "Apply Patch", "impact": "Information Disclosure"}, "threat_synthesis": {"affected_systems": "The flaw affects Microsoft XML Notepad running on Windows platforms. Any installation of XML Notepad before version 2.9.0.21 is susceptible. The issue applies to the default configuration where DTD processing remains enabled.", "description_and_impact": "XML Notepad provides an interface for XML documents. Prior to version 2.9.0.21 it does not disable DTD processing by default, which allows external entities to be automatically resolved. An attacker can craft a malicious XML file containing a DTD that causes XML Notepad to make outbound HTTP or SMB requests, potentially leaking local file contents or capturing cached NTLM credentials. The vulnerability is classified under CWE\u2011611, exposing sensitive data.", "risk_and_exploitability": "The CVSS base score is 6.5, indicating moderate severity. EPSS shows a less than 1% chance of exploitation in the next year, and the flaw is not listed in the CISA KEV catalog. The likely attack vector is that a user must open a crafted XML file in XML Notepad; the vulnerability is local and does not require network access to the attacker. Exploitability is limited to contexts where the user has permission to access the file, but once triggered it can exfiltrate arbitrary file contents or capture session credentials."}}}}, "created": "2026-04-02T07:52:16.963588+00:00", "updated": "2026-04-14T16:42:15.131084+00:00", "vendors": ["microsoft", "microsoft$PRODUCT$xmlnotepad"]}