What is the CVSS score of CVE-2025-21391?

CVE-2025-21391 has a CVSS 3.1 base score of 7.1 (High). CVSS vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H. EPSS exploitation probability: 5.6%.

Is CVE-2025-21391 being actively exploited?

Yes, CVE-2025-21391 is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, confirming active in-the-wild exploitation. Immediate patching is required.

How to fix or mitigate CVE-2025-21391?

Within 24 hours: Identify all affected systems and apply vendor patches immediately. Vendor patch is available.

Windows 10 1507 CVE-2025-21391

HIGH

Improper Link Resolution Before File Access (CWE-59)

2025-02-11 secure@microsoft.com

Information Disclosure Microsoft Windows 10 1507 Windows 10 1607 Windows 10 1809 Windows 10 21h2 Windows 10 22h2 Windows 11 22h2 Windows 11 23h2 Windows 11 24h2 Windows Server 2016 Windows Server 2019 Windows Server 2022 Windows Server 2022 23h2 Windows Server 2025

7.1

CVSS 3.1 · Vendor: microsoft

View

Vulnerability Assessment

Weakness	CWE CWE-59 OWASP Top 10:2025 A01:2025 - Broken Access Control ASVS 5.0 V5 - File Handling Symlink resolution safety
Impact	High risk (CVSS 7.1). File deletion vulnerabilities can be escalated to full privilege escalation through techniques like DLL hijacking (deleting a system DLL and replacing it with a malicious one).
Exploit ScenarioDerived	An attacker creates a symlink pointing from a user-writable location to a system DLL. Windows Storage follows the symlink and deletes the system file. The attacker then places a malicious DLL in the vacated location, which is loaded by a SYSTEM process.

Act Now Prioritize within 24-48h. Why: In CISA KEV with patch available.

Exploited in the wild (CISA KEV) Patch available 5.6% exploitation probability (EPSS)

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AnalysisAIv1 – Mar 28, 2026

Windows Storage contains an elevation of privilege vulnerability through symlink following that allows authorized attackers to delete targeted files, enabling privilege escalation.

Earlier versions of this analysis (1)

v1 Mar 28, 2026 - 18:26 CVSS 7.1

A symlink-following vulnerability in Windows Storage allows local attackers to delete arbitrary files by creating symbolic links, which can be leveraged for privilege escalation.

RemediationAI

Apply Microsoft security update. Monitor for suspicious symlink creation in user-writable directories.

Affects your stack

Find out whether the stacks and servers you run are on an affected version.

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

Technical ContextAI · show details

The CWE-59 improper link resolution allows a local attacker to create symbolic links that redirect Windows Storage operations to delete files in privileged locations. By targeting specific system files, the attacker can create conditions for privilege escalation.

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Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

Vendor (microsoft) PRIMARY 7.1 HIGH

AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H

Primary rating from Vendor (microsoft) · only source for this CVE.

CVSS VectorVendor: microsoft

Attack Vector

Local

Attack Complexity

Low

Privileges Required

Low

User Interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

High

Availability

High

Lifecycle Timeline

Patch released

Mar 28, 2026 - 18:26 nvd

Patch available

Added to CISA KEV

Oct 27, 2025 - 17:13 cisa

CISA KEV

CVE Published

Feb 11, 2025 - 18:15 nvd

HIGH 7.1

DescriptionCVE.org

Windows Storage Elevation of Privilege Vulnerability

Executive ViewAI

Why It Matters

CVE-2025-21391 presents moderate security risk rated CVSS 7.1. Exploitation could compromise the security of affected deployments. This vulnerability is actively exploited in the wild (KEV-listed) and requires immediate remediation. A patch is available and should be applied as part of regular vulnerability management.

Business Impact: Severe

Compensating Controls

Apply vendor patch. If immediate patching is not feasible: (1) Implement network-level access controls to limit exposure; (2) Enable enhanced monitoring and alerting; (3) Apply principle of least privilege.

Threat Intelligence Overview

EPSS Score

5.6%

Top 10% exploitable

Data Quality

4 sources

Confidence: Medium

NVD

CVE.org

CISA KEV

EPSS

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue

Severity HIGH

CISA KEV Yes

Public POC No

EPSS 5.6%

Patch available Yes

Active threat Yes

Deciding rule

In CISA KEV with patch available

What every action level means

Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.

Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.

This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.

This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.

Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived

Out-of-Cycle

Exploitation· derived

Active

System Exposure· derived

Small

Automatable· derived

Human Impact

Very High

Priority Score

Low Medium High Critical

KEV: +50

EPSS: +6

CVSS: +36

PoC: 0

Weaponized: 0

Threat intel: 0

Gov advisory: 0

Attack Technique

Information Disclosure MEDIUM

Information disclosure occurs when an application unintentionally exposes sensitive data that aids attackers in reconnaissance or directly compromises security.

Affected Products (CPE)CVE.org

cpe:2.3:o:microsoft:windows_10_1507:*:*:*:*:*:*:x64:*

cpe:2.3:o:microsoft:windows_10_1507:*:*:*:*:*:*:x86:*

cpe:2.3:o:microsoft:windows_10_1607:*:*:*:*:*:*:x64:*

cpe:2.3:o:microsoft:windows_10_1607:*:*:*:*:*:*:x86:*

cpe:2.3:o:microsoft:windows_10_1809:*:*:*:*:*:*:x64:*

cpe:2.3:o:microsoft:windows_10_1809:*:*:*:*:*:*:x86:*

cpe:2.3:o:microsoft:windows_10_21h2:*:*:*:*:*:*:*:*

cpe:2.3:o:microsoft:windows_10_22h2:*:*:*:*:*:*:*:*

cpe:2.3:o:microsoft:windows_11_22h2:*:*:*:*:*:*:*:*

cpe:2.3:o:microsoft:windows_11_23h2:*:*:*:*:*:*:*:*

cpe:2.3:o:microsoft:windows_11_24h2:*:*:*:*:*:*:*:*

cpe:2.3:o:microsoft:windows_server_2016:*:*:*:*:*:*:*:*

cpe:2.3:o:microsoft:windows_server_2019:*:*:*:*:*:*:*:*

cpe:2.3:o:microsoft:windows_server_2022:*:*:*:*:*:*:*:*

cpe:2.3:o:microsoft:windows_server_2022_23h2:*:*:*:*:*:*:*:*

cpe:2.3:o:microsoft:windows_server_2025:*:*:*:*:*:*:*:*

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References

Advisories & patches

PATCH https://msrc.microsoft.com/update-guide/vulnerability/CVE-2025-21391 REF https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2025-21391

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