High 7.8Published Jul 14, 2026

CVE-2026-55039Microsoft Excel Remote Code Execution Vulnerability

Updated under an hour ago (Oct 27, 2026, 12:40 PM ET)

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It affects Microsoft 365 Apps for Enterprise and 13 other products. Add what you run to find out whether that includes you.

No exploitation reported and no EPSS estimate yet.

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Exploited in the last 30 days

Integer underflow (wrap or wraparound) in Microsoft Office Excel allows an unauthorized attacker to execute code locally.

CVSS: 7.8 HIGH (v3.1, CNA)CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C
Weakness (CWE): CWE-191, CWE-122
Known exploited: Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days): Not loaded for this CVE
Assigned by: microsoft
NVD analysis: Analyzed
Record last updated: Oct 8, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

Microsoft Microsoft 365 Apps for Enterprise microsoft:365_apps_for_enterprise (from the name)	from 16.0.1 before https://aka.ms/OfficeSecurityReleases	CNA record
Microsoft Microsoft Excel 2016 microsoft:excel_2016 (from the name)	from 16.0.0.0 before 16.0.5561.1001	CNA record
Microsoft Microsoft Office 2019 microsoft:office_2019 (from the name)	from 19.0.0 before https://aka.ms/OfficeSecurityReleases	CNA record
Microsoft Microsoft Office 365 for Mac microsoft:office_365_for_mac (from the name)	from 1.0.0 before 16.111.26071215	CNA record
Microsoft Microsoft Office LTSC 2021 microsoft:office_ltsc_2021 (from the name)	from 16.0.1 before https://aka.ms/OfficeSecurityReleases	CNA record
Microsoft Microsoft Office LTSC 2024 microsoft:office_ltsc_2024 (from the name)	from 16.0.0 before https://aka.ms/OfficeSecurityReleases	CNA record
Microsoft Microsoft Office LTSC for Mac 2021 microsoft:office_ltsc_for_mac_2021 (from the name)	from 16.0.1 before 16.111.26071215	CNA record
Microsoft Microsoft Office LTSC for Mac 2024 microsoft:office_ltsc_for_mac_2024 (from the name)	from 16.0.0 before 16.111.26071215	CNA record
Microsoft Office Online Server microsoft:office_online_server (from the name)	from 16.0.0.0 before 16.0.10417.20175	CNA record
microsoft 365_apps microsoft:365_apps	all versions; all versions	NVD
1–10 of 16

References

References

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-55039	vendor-advisory, patch

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.