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CVE-2026-56156: Microsoft Excel Remote Code Execution Vulnerability

highCVSS 7.8CVE-2026-56156
Heap-based buffer overflow in Microsoft Office Excel allows an unauthorized attacker to execute code locally.

CSIRTS triage

vendor: Microsoftproduct: ExcelRemote code execution
What
Heap-based buffer overflow in Microsoft Office Excel allows unauthorized code execution locally.
Who is affected
Deployments of Microsoft Office Excel.
Urgency
Remediation is high priority due to the high severity and potential for local code execution.
Action
Update Microsoft Office Excel to the latest version.

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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-2026-56156

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-2026-56156coverage & exploitation statusNVD · CVE.org

Same CVEs, other sources

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

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