CVE-2025-21391
Microsoft — Microsoft Windows Storage Link Following Vulnerability
CISA KEV · in the CISA KEV catalog since 2025-02-11
What EVULNABLE says
Listed in the CISA KEV catalog, and an EPSS probability of 0.023.
Patch This Cycle
The priority band answers “how soon”, not “how bad” — see Methodology for what it weighs and where it abstains.
The evidence behind it
| Measure | Value | Source | What it means |
|---|---|---|---|
| CVSS base score | 7.1 | NVD | How severe the flaw is in itself. It does not say how likely an attack is. |
| FIRST EPSS | 0.023 (83rd pctl) | FIRST | FIRST's estimate of the chance this is exploited in the next 30 days, and how that ranks against all CVEs. |
| Actively exploited | Confirmed | CISA KEV | Whether a source of record has confirmed attacks using it in the wild. |
| Ransomware campaign use | Unknown or none | CISA KEV | Whether CISA has seen ransomware operators use it. |
| CISA remediation deadline | 2025-03-04 — KEV since 2025 · listed over a year | CISA KEV | The date US federal agencies must have fixed or mitigated it. |
| Fixed in | windows 10 1507: update to 10.0.10240.20915 or later | windows 10 1607: update to 10.0.14393.7785 or later | windows 10 1809: update to 10.0.17763.6893 or later | windows 10 21h2: update to 10.0.19044.5487 or later | windows 10 22h2: update to 10.0.19045.5487 or later | windows 11 22h2: update to 10.0.22621.4890 or later | NVD | The version(s) the vendor has published as fixed, where NVD records one. |
| Public exploit module | None known | Metasploit | Module existing is not the same as active exploitation. |
| EUVD cross-reference | Listed | ENISA EUVD | ENISA's own vulnerability database entry for this CVE, where one exists. |
Impacted software or hardware
- windows 10 1507 Operating system — < 10.0.10240.20915
- windows 10 1607 Operating system — < 10.0.14393.7785
- windows 10 1809 Operating system — < 10.0.17763.6893
- windows 10 21h2 Operating system — < 10.0.19044.5487
- windows 10 22h2 Operating system — < 10.0.19045.5487
- windows 11 22h2 Operating system — < 10.0.22621.4890
- windows 11 23h2 Operating system — < 10.0.22631.4890
- windows 11 24h2 Operating system — < 10.0.26100.3107
+5 more affected products — see the full list at NVD.
Fixed versions: windows 10 1507: update to 10.0.10240.20915 or later | windows 10 1607: update to 10.0.14393.7785 or later | windows 10 1809: update to 10.0.17763.6893 or later | windows 10 21h2: update to 10.0.19044.5487 or later | windows 10 22h2: update to 10.0.19045.5487 or later | windows 11 22h2: update to 10.0.22621.4890 or later
Remediation: Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.
Remediation basis: CISA KEV required action
ENISA EUVD also lists this CVE at CVSS 7.1 (v3.1), assigned by microsoft. Source: euvd.enisa.europa.eu.
What CISA says to do
The primary records
This page is an opinion about urgency. Where it and a source of record disagree, the source of record is the record.
Where this sits
CVE-2025-21391 is a Microsoft entry in the CISA KEV catalog. The priority feed ranks Microsoft's current monthly release rather than older Microsoft CVEs, so this one is not listed there; the page above scores it from the same sources.