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CVE-2026-44820: Microsoft Excel Remote Code Execution Vulnerability

highCVSS 7.8CVE-2026-44820
Integer underflow (wrap or wraparound) in Microsoft Office Excel allows an unauthorized attacker to execute code locally.

CSIRTS triage

vendor: Microsoftproduct: Microsoft ExcelRemote code execution
What
This vulnerability allows an unauthorized attacker to execute code locally via an integer underflow.
Who is affected
Deployments of Microsoft Excel.
Urgency
Remediation is high urgency due to the high severity rating.
Action
Patch Microsoft Excel for CVE-2026-44820.

AI-assisted analysis generated from the source advisory — verify against the original.

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Details

Source
Microsoft Security Response Center (INTL · vendor-psirt · site)
Severity
high — CVSS 7.8
Published
2026-06-09
Exploitation
Not in CISA KEV at last sync

Original advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-44820

Exploitation outlook

EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.

Referenced CVEs

CVECSIRTS overviewExternal
CVE-2026-44820coverage & exploitation statusNVD · CVE.org

Recent advisories for Microsoft Excel Remote

A cluster of recent advisories against the same product widens the attack surface — attackers routinely chain freshly published CVEs on one product, so review these together.

More from Microsoft Security Response Center