Patch tracker / CVE reference / CVE-2026-40366
CVE-2026-40366
Updated July 21, 2026. Data refreshed on every build from MSRC, CISA KEV, and FIRST EPSS.
High severity Microsoft vulnerability, CVSS 8.4. Fixed by 1 Microsoft security update.
All about CVE-2026-40366: the Senserva AI read, whether it is exploited, the official patches, its change history, and the questions admins ask.
CVE-2026-40366 is a high severity Microsoft vulnerability with a CVSS score of 8.4. Microsoft has shipped the fix: deploy the update below from the Microsoft Update Catalog, and see where this CVE sits against the rest on the patch tracker.
Risk summary
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Senserva AI Opinion for CVE-2026-40366
Another Word parsing flaw from the same batch as CVE-2026-40364, with the same shape: Office 2019 and Microsoft 365 Apps affected, code execution when a crafted document is opened, EPSS at 4 percent. Attackers rarely need more than one working document exploit, so paired fixes like these should ship together.
Do this: Deploy the full Office security update rather than cherry-picking individual Word fixes.
AI-generated from public data, 2026-07-07. Verify against the vendor advisory before acting.
Senserva AI Opinion and rich prompt for CVE-2026-40366
Copy this prompt into Claude, ChatGPT, or Copilot. The facts are included, sourced from this page.
Full tracking and change history for CVE-2026-40366
Published and last-revised dates are authoritative, from Microsoft MSRC (or the CISA KEV date-added). Senserva additionally records day-to-day changes from 2026-07-07, refreshed several times a day; the change count reflects that forward-only tracking.
Exploitation and severity
Not in the CISA KEV catalog. EPSS exploit probability 4.4%. CVSS 8.4 (High).
This CVE is among the lower half of tracked Microsoft CVEs by EPSS exploit probability.
Official patch(es) for CVE-2026-40366
Moderate priority: schedule it in your normal patch cycle. In Intune or Defender, confirm whether the fixing update KB5002858 are installed across the affected products. Senserva does this automatically across your tenant and flags every missing patch.
Apply the Microsoft security update below to fix CVE-2026-40366. Each KB page carries the Microsoft Update Catalog download, Microsoft's known issues for the update, a copy-paste PowerShell check for whether it is installed, and the Senserva AI read.
Affected products
Common questions about CVE-2026-40366
Is CVE-2026-40366 actively exploited?
It is not currently listed in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score puts the probability of exploitation in the next 30 days at 4.4%.
What patch fixes CVE-2026-40366?
Microsoft fixed CVE-2026-40366 in KB5002858. Download from the Microsoft Update Catalog, or let Intune, Windows Update, or WSUS deliver it.
Which products are affected by CVE-2026-40366?
Microsoft 365 Apps for Enterprise for 32-bit Systems, Microsoft Office 2019 for 32-bit editions, Microsoft Office 2019 for 64-bit editions.
Can I ask my own AI about CVE-2026-40366?
Yes. This page includes a free, ready-to-paste AI prompt containing CVE-2026-40366's key facts: severity, CVSS, EPSS exploit probability, CISA KEV status, and the fixing KB. Copy it into Claude, ChatGPT, or Copilot for a triage plan; the data is refreshed three times a day (5 AM, 12:30 PM, and 7 PM US Central).
Fixed by the same update
If you are patching CVE-2026-40366, the same update also fixes these:
Authoritative references
Want every Microsoft CVE and the patches that fix it, ranked by real-world risk? See the Microsoft Patch Tracker.
