CVE-2026-64909: Microsoft Office Remote Code Execution Vulnerability
Integer underflow (wrap or wraparound) in Microsoft Office allows an unauthorized attacker to execute code locally.
CSIRTS triage
- What
- An integer underflow vulnerability in Microsoft Office allows execution of arbitrary code locally.
- Who is affected
- Users running affected versions of Microsoft Office on Windows.
- Urgency
- High severity (CVSS 7.8) with code execution capability; remediation should be prioritized.
- Action
- Apply the latest security patch for Microsoft Office from Microsoft Update.
AI-assisted analysis generated from the source advisory — verify against the original.
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Details
Original advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-64909
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.
- Low exploitation riskCVE-2026-649090.34% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 27% of all EPSS-scored CVEs.
Referenced CVEs
| CVE | CSIRTS overview | External |
|---|---|---|
| CVE-2026-64909 | coverage & exploitation status | NVD · CVE.org |
Same CVEs, other sources
How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.
- high[NEW] [high] Microsoft Office Products: Multiple Vulnerabilitiescert-bund
- unknownMultiple vulnerabilities in Microsoft Office (August 12, 2026)cert-fr-avis
- unknownNCSC-2026-0286 [1.00] [M/H] Vulnerabilities patched in Microsoft Officencsc-nl
- highCVE-2026-64909: Integer underflow (wrap or wraparound) in Microsoft Office allows an unauthorized attacker to …nvd
Recent advisories for Microsoft Office 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.
- highCVE-2026-63518: Microsoft Office Word Remote Code Execution Vulnerabilitymsrc · 2026-08-11
- highCVE-2026-65656: Microsoft Office Remote Code Execution Vulnerabilitymsrc · 2026-08-11
- highCVE-2026-64915: Microsoft Office Word Remote Code Execution Vulnerabilitymsrc · 2026-08-11
- highCVE-2026-70130: Microsoft Office Remote Code Execution Vulnerabilitymsrc · 2026-08-11
- highCVE-2026-66807: Microsoft Office Graphics Component Remote Code Execution Vulnerabilitymsrc · 2026-08-11
- highCVE-2026-63525: Microsoft Office Word Remote Code Execution Vulnerabilitymsrc · 2026-08-11
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