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CVE-2026-55039: Microsoft Excel Remote Code Execution Vulnerability

highCVSS 7.8CVE-2026-55039
Integer underflow (wrap or wraparound) in Microsoft Office Excel allows an unauthorized attacker to execute code locally.

CSIRTS triage

vendor: Microsoftproduct: Microsoft ExcelRemote code executionOther
What
Integer underflow in Microsoft Office Excel allows an unauthorized attacker to execute code locally.
Who is affected
Users of Microsoft Excel.
Urgency
Remediation is urgent due to the high severity and potential for remote code execution.
Action
Apply the latest security updates for Microsoft Excel.

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
2026-07-14
Exploitation
Not in CISA KEV at last sync

Original advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-55039

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-2026-55039coverage & exploitation statusNVD · CVE.org

Same CVEs, other sources

How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.

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