Patch tracker / CVE reference / CVE-2025-21391
CVE-2025-21391
CVE-2025-21391 is a high severity Microsoft vulnerability with a CVSS score of 8.8. It is in the CISA Known Exploited Vulnerabilities catalog: attackers are using it in the wild, which makes it a fix-first item. Microsoft has shipped the fix: deploy one of the 10 updates below from the Microsoft Update Catalog, and see where this CVE sits against the rest on the patch tracker.
High severity Microsoft vulnerability, CVSS 8.8. Fixed by 10 Microsoft security updates.
Risk summary
Updated July 24, 2026. Data refreshed on every build from MSRC, CISA KEV, and FIRST EPSS.
Senserva AI Opinion for CVE-2025-21391
Windows Storage is the vector for this elevation of privilege flaw, exploited in the wild and KEV-listed on 2025-02-11 at CVSS 8.8. Storage-stack escalations often let attackers manipulate or delete protected files to gain higher privileges, and the component exists on every affected Windows 10 1809 and Server 2019 machine.
Do this: Verify February 2025 cumulative update coverage and investigate unexplained file deletions on any late-patched host.
AI-generated from public data, 2026-07-07. Verify against the vendor advisory before acting.
Senserva AI Opinion and rich prompt for CVE-2025-21391
Copy this prompt into Claude, ChatGPT, or Copilot. The facts are included, sourced from this page.
Full tracking and change history for CVE-2025-21391
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
Listed in the CISA Known Exploited Vulnerabilities catalog, confirmed exploited in the wild. EPSS exploit probability 24%. CVSS 8.8 (High).
This CVE is among the top half of tracked Microsoft CVEs by EPSS exploit probability, and one of 2 actively-exploited CVEs in February 2025.
Official patch(es) for CVE-2025-21391
Treat as urgent: it is being exploited in the wild (CISA KEV), so patch ahead of items that are not. In Intune or Defender, confirm whether the fixing updates KB5051974, KB5051979, KB5051980, KB5051987, KB5051989, KB5052000, KB5052006, KB5052040, KB5052105, KB5052106 are installed across the affected products. Senserva does this automatically across your tenant and flags every missing patch.
Apply the Microsoft security updates below to fix CVE-2025-21391. 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-2025-21391
Is CVE-2025-21391 actively exploited?
Yes. CVE-2025-21391 is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, which means exploitation in the wild has been confirmed. Its EPSS exploit probability is 24%.
What patch fixes CVE-2025-21391?
Microsoft fixed CVE-2025-21391 in KB5051974, KB5051979, KB5051980, KB5051987, KB5051989, KB5052000, KB5052006, KB5052040, KB5052105, KB5052106. Download from the Microsoft Update Catalog, or let Intune, Windows Update, or WSUS deliver it.
Which products are affected by CVE-2025-21391?
Windows 10 Version 1809 for 32-bit Systems, Windows 10 Version 1809 for x64-based Systems, Windows Server 2019.
Can I ask my own AI about CVE-2025-21391?
Yes. This page includes a free, ready-to-paste AI prompt containing CVE-2025-21391'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 updates
If you are patching CVE-2025-21391, the same updates also fix these:
Authoritative references
Want every Microsoft CVE and the patches that fix it, ranked by real-world risk? See the Microsoft Patch Tracker.
