CVE-2026-40421

MEDIUM

Published May 12, 2026 Modified May 16, 2026 CWE-73

Description

External control of file name or path in Microsoft Office Word allows an unauthorized attacker to disclose information over a network.

CVSS v3.1 Score

4.3

MEDIUM

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N

EPSS — Exploit Prediction

0.0005

Probability of exploitation

0.17%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-73 CWE-73

Affected Products

Vendor	Product	Versions
microsoft	365_apps	All
microsoft	365_apps	All
microsoft	office	All
microsoft	office	All
microsoft	office	All
microsoft	office	All
microsoft	office	All
microsoft	office	All
microsoft	word	All
microsoft	word	All

References

Advisories & Patches

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-40421

Frequently Asked Questions

What is CVE-2026-40421? +

External control of file name or path in Microsoft Office Word allows an unauthorized attacker to disclose information over a network. It has a CVSS v3.1 base score of 4.3 (MEDIUM).

How severe is CVE-2026-40421? +

CVE-2026-40421 has a CVSS v3.1 score of 4.3 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance. The EPSS score is 0.0005, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-40421? +

CVE-2026-40421 affects products from microsoft, specifically: 365_apps, office, word. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-40421? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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