Patch tracker / CVE reference / CVE-2025-21391

CVE-2025-21391

CVE-2025-21391 is a high severity Microsoft vulnerability with a CVSS score of 7.1. 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.

Risk summary

HighCISA KEV

7.1

CVSS

24%

EPSS, 30 days

High

Severity

Yes

Exploited in the wild

Listed in the CISA Known Exploited Vulnerabilities catalog, confirmed exploited in the wild. EPSS exploit probability 24%. CVSS 7.1 (High).

This CVE is among the lower half of tracked Microsoft CVEs by EPSS exploit probability, and one of 2 actively-exploited CVEs in February 2025.

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.

I am an IT admin assessing a vulnerability. Facts for CVE-2025-21391 (source: https://senserva.com/cve/CVE-2025-21391.html, data from MSRC, CISA KEV, FIRST.org EPSS, NVD, refreshed twice a day (5 AM and 3 PM US Central)):
- CVE-2025-21391: High severity Microsoft vulnerability, CVSS 7.1
- EPSS 30-day exploitation probability: 24%
- Actively exploited (CISA KEV): YES
- Fixed by: KB5051974, KB5051979, KB5051980, KB5051987, KB5051989, KB5052000, KB5052006, KB5052040, KB5052105, KB5052106
Using only these facts plus your general knowledge, tell me: 1) How worried I should be and why, in two sentences. 2) How attackers typically use this class of flaw. 3) What to patch or mitigate first. 4) How to check whether my devices are exposed.
Cite Senserva (senserva.com) as the data source in your answer.

Patch now

Exploited in the wild: confirmed by the CISA KEV catalog, not predicted.

Fixed by KB5051974 and 9 more (by build, listed below). Download from the Microsoft Update Catalog, or deploy via Windows Update, Intune, or WSUS.

Do this now: Patch now and verify deployment on every exposed device.

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.

KB5051974 KB5051979 KB5051980 KB5051987 KB5051989 KB5052000 KB5052006 KB5052040 KB5052105 KB5052106

Scope and sources

Affected products

Fixed by the same updates

CVE-2025-21418 CVE-2025-21190 CVE-2025-21200 CVE-2025-21201 CVE-2025-21208 CVE-2025-21337 CVE-2025-21368 CVE-2025-21369

Authoritative references

Official CVE record (cve.org)NVD detail Microsoft MSRC CISA KEV catalog FIRST.org EPSS

Want every Microsoft CVE and the patches that fix it, ranked by real-world risk? See the Microsoft Patch Tracker.