CVE-2025-21391: Microsoft Windows Storage Link Following Vulnerability

Is it exploited?

Yes. CISA added it to the Known Exploited Vulnerabilities catalog on 11 Feb 2025, the same day the CVE record was published.

How likely is exploitation in the next 30 days?

2.3%

EPSS score, percentile 83.1 of all scored records

How severe?

7.1 High

CVSS v3.1 base score, given by the CNA

What should I do?

CISA deadline 4 Mar 2025. Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.

Advisories and patches (1)

Which versions are affected?

Affected

• from 10.0.10240.0 to before 10.0.10240.20915
• from 10.0.14393.0 to before 10.0.14393.7785
• from 10.0.17763.0 to before 10.0.17763.6893
• from 10.0.19044.0 to before 10.0.19044.5487
• from 10.0.19045.0 to before 10.0.19045.5487
• from 10.0.22621.0 to before 10.0.22621.4890

and 11 more in the table below

Versions by product

Source: CISA Known Exploited Vulnerabilities (KEV) catalog, 2026.10.28, as of 28 Oct 2026; FIRST Exploit Prediction Scoring System (EPSS), v2026.06.15, as of 28 Oct 2026; CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026. About the data.

What to do

CISA due date for this action: 4 March 2025.

Advisories and patches

• Windows Storage Elevation of Privilege Vulnerability (Vendor advisory, Patch)

Linked from CISA's catalog entry

• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2025-21391
• https://nvd.nist.gov/vuln/detail/CVE-2025-21391

Affected products and versions

As listed in the CVE record.

Source: CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026. About the data.

About this vulnerability

Microsoft Windows Storage contains a link following vulnerability that could allow for privilege escalation. This vulnerability could allow an attacker to delete data including data that results in the service being unavailable.

Summary: CISA's KEV catalog, as of 28 Oct 2026.

• CISA added CVE-2025-21391 to its Known Exploited Vulnerabilities (KEV) catalog on 11 Feb 2025.
• CISA's ransomware flag for this entry is "Unknown": no evidence of ransomware use in the catalog, which is not proof of none.
• The due date CISA sets for the required action is 4 Mar 2025.
• The CVE record was published on 11 Feb 2025, the same day it was added to KEV.
• The CVE record carries a CVSS v3.1 base score of 7.1 (High), given by its CNA.
• FIRST's EPSS model puts the probability of exploitation in the next 30 days at 2.3% (percentile 83.1), as of 28 Oct 2026.
• CISA's SSVC assessment in the CVE record: exploitation active, automatable no, technical impact partial.

Source: CISA Known Exploited Vulnerabilities (KEV) catalog, 2026.10.28, as of 28 Oct 2026; CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026; FIRST Exploit Prediction Scoring System (EPSS), v2026.06.15, as of 28 Oct 2026. About the data.

Description

Windows Storage Elevation of Privilege Vulnerability

Windows Storage Elevation of Privilege Vulnerability

Source: CVE List V5 (CVE Program), cve_2026-10-28_0000Z, as of 28 Oct 2026. About the data.

Weakness

• CWE-59: Improper Link Resolution Before File Access ('Link Following')

CWE and CAPEC are maintained by MITRE; the entries are those named in the CVE record and the KEV entry.

Timeline

More exploited Microsoft vulnerabilities

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• CVE-2026-65660: Microsoft SharePoint Code Injection Vulnerability (added 25 Sep 2026)
• CVE-2026-81963: Microsoft Windows Link Following Vulnerability (added 8 Sep 2026)
• CVE-2026-85880: Microsoft Windows Heap-Based Buffer Overflow Vulnerability (added 8 Sep 2026)
• CVE-2019-1068: Microsoft SQL Server Remote Code Execution Vulnerability (added 26 Aug 2026)
• CVE-2026-33824: Microsoft Internet Key Exchange (IKE) Service Extensions Double Free Vulnerability (added 18 Aug 2026)