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CVE-2026-21511

HIGHCVSS 7.5/10EPSS 3.64%

Last modified

CVE-2026-21511 is a high-severity vulnerability rated 7.5/10 on the CVSS scale. Deserialization of untrusted data in Microsoft Office Outlook allows an unauthorized attacker to perform spoofing over a network.. EPSS estimates a 3.64% chance of exploitation in the next 30 days.

Description

Deserialization of untrusted data in Microsoft Office Outlook allows an unauthorized attacker to perform spoofing over a network.

Metrics

CVSS 3.1
7.5/10

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

EPSS Probability
3.64%

88.1th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

VendorProductVersions
Microsoft365 AppsAll versions
MicrosoftOffice2019
MicrosoftOffice Long Term Servicing Channel2021
MicrosoftOffice Long Term Servicing Channel2024
MicrosoftSharepoint Server< 16.0.19127.20518
MicrosoftSharepoint Server2016
MicrosoftSharepoint Server2019
MicrosoftWord2016

References

Timeline

Published
Last Modified
Status
Analyzed

Frequently Asked Questions

What is CVE-2026-21511?
Deserialization of untrusted data in Microsoft Office Outlook allows an unauthorized attacker to perform spoofing over a network.
How severe is CVE-2026-21511?
CVE-2026-21511 has a CVSS score of 7.5/10 (HIGH severity). The EPSS model estimates a 3.64% probability of exploitation in the next 30 days.
How do I fix CVE-2026-21511?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2026-21511?

Run a free Strix scan to check your systems for this vulnerability.

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Source: NVD / NIST