How severe is CVE-2026-34401?

CVE-2026-34401 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is high, integrity none, and availability none.

Is CVE-2026-34401 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (58th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-34401?

CVE-2026-34401 affects Microsoft Xml Notepad. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-34401?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

Does CVE-2026-34401 have an EU (EUVD) identifier?

Yes. CVE-2026-34401 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-17666.

When was CVE-2026-34401 published?

CVE-2026-34401 was published on 2026-03-31 and last updated on 2026-06-17.

CVE-2026-34401

CVE-2026-34401 is a medium-severity vulnerability in Microsoft Xml Notepad with a CVSS 3.x base score of 6.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-611.

Key facts

Severity: Medium (CVSS 3.x base score 6.5)
EPSS exploit prediction: 1% (58th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-17666
Weakness: CWE-611
Affected product: Microsoft Xml Notepad
Published: 2026-03-31
Last modified: 2026-06-17

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.

Frequently asked questions

What is 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 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.
How severe is CVE-2026-34401?: CVE-2026-34401 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is high, integrity none, and availability none.
Is CVE-2026-34401 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (58th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-34401?: CVE-2026-34401 affects Microsoft Xml Notepad. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-34401?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2026-34401 have an EU (EUVD) identifier?: Yes. CVE-2026-34401 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-17666.
When was CVE-2026-34401 published?: CVE-2026-34401 was published on 2026-03-31 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:microsoft:xml_notepad:*:*:*:*:*:windows:*:*

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