CyberSecBulletin
CVE-2025-21391Exploited in the wildNVD status: Analyzed

Microsoft Windows Storage Link Following

Published Updated By the CyberSecBulletin desk

CVE-2025-21391 is a high-severity improper link resolution before file access vulnerability in Windows 10 Version 1507 from Microsoft, with a CVSS 3.1 base score of 7.1 out of 10. It can be exploited with local access to the system by an attacker with a low-privileged account, without any action from a user. The record lists version 10.0.10240.20915 as the first without the flaw, so updating Windows 10 Version 1507 to that release or later removes the exposure. CISA added it to the Known Exploited Vulnerabilities catalogue on February 11, 2025, which means attacks have been observed in the wild.

Patch now

Attackers are already exploiting this vulnerability, according to CISA.

What to do

  1. Update Windows 10 Version 1507 to 10.0.10240.20915 or a later version.
  2. Update Windows 10 Version 1607 to 10.0.14393.7785 or a later version.
  3. Update Windows 10 Version 1809 to 10.0.17763.6893 or a later version.
  4. CISA's required action: Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.
  5. Read the advisory on msrc.microsoft.com for workarounds and exact fixed builds.

Affected products and versions

VendorProductAffected versionsFixed in
MicrosoftWindows 10 Version 150710.0.10240.0 up to, but not including, 10.0.10240.2091510.0.10240.20915
MicrosoftWindows 10 Version 160710.0.14393.0 up to, but not including, 10.0.14393.778510.0.14393.7785
MicrosoftWindows 10 Version 180910.0.17763.0 up to, but not including, 10.0.17763.689310.0.17763.6893
MicrosoftWindows 10 Version 21H210.0.19044.0 up to, but not including, 10.0.19044.548710.0.19044.5487
MicrosoftWindows 10 Version 22H210.0.19045.0 up to, but not including, 10.0.19045.548710.0.19045.5487
MicrosoftWindows 11 version 22H210.0.22621.0 up to, but not including, 10.0.22621.489010.0.22621.4890
MicrosoftWindows 11 version 22H310.0.22631.0 up to, but not including, 10.0.22631.489010.0.22631.4890
MicrosoftWindows 11 Version 23H210.0.22631.0 up to, but not including, 10.0.22631.489010.0.22631.4890
MicrosoftWindows 11 Version 24H210.0.26100.0 up to, but not including, 10.0.26100.319410.0.26100.3194
MicrosoftWindows Server 201610.0.14393.0 up to, but not including, 10.0.14393.778510.0.14393.7785
MicrosoftWindows Server 2016 (Server Core installation)10.0.14393.0 up to, but not including, 10.0.14393.778510.0.14393.7785
MicrosoftWindows Server 201910.0.17763.0 up to, but not including, 10.0.17763.689310.0.17763.6893
MicrosoftWindows Server 2019 (Server Core installation)10.0.17763.0 up to, but not including, 10.0.17763.689310.0.17763.6893
MicrosoftWindows Server 202210.0.20348.0 up to, but not including, 10.0.20348.320710.0.20348.3207
MicrosoftWindows Server 2022, 23H2 Edition (Server Core installation)10.0.25398.0 up to, but not including, 10.0.25398.142510.0.25398.1425
MicrosoftWindows Server 202510.0.26100.0 up to, but not including, 10.0.26100.319410.0.26100.3194
MicrosoftWindows Server 2025 (Server Core installation)10.0.26100.0 up to, but not including, 10.0.26100.319410.0.26100.3194
MicrosoftWindows 10 1507before 10.0.10240.2091510.0.10240.20915
MicrosoftWindows 10 1607before 10.0.14393.778510.0.14393.7785
MicrosoftWindows 10 1809before 10.0.17763.689310.0.17763.6893
MicrosoftWindows 10 21h2before 10.0.19044.548710.0.19044.5487
MicrosoftWindows 10 22h2before 10.0.19045.548710.0.19045.5487
MicrosoftWindows 11 22h2before 10.0.22621.489010.0.22621.4890
MicrosoftWindows 11 23h2before 10.0.22631.489010.0.22631.4890
MicrosoftWindows 11 24h2before 10.0.26100.310710.0.26100.3107

Version data comes from the organisation that assigned the CVE; 1 further products are omitted here. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
LocalThe attacker needs local access or must trick a user into running something.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
LowA basic user account is enough.
User interaction
NoneNo action by a victim is required.
Scope
UnchangedImpact stays within the vulnerable component.
Confidentiality
NoneNo data is disclosed.
Integrity
HighData or code can be modified at will.
Availability
HighThe component can be taken down completely.

Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H. Scored by CNA (microsoft.com).

Official description

Windows Storage Elevation of Privilege Vulnerability

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Improper Link Resolution Before File Access

The product attempts to access a file based on the filename, but it does not properly prevent that filename from identifying a link or shortcut that resolves to an unintended resource.

How developers prevent this class of flaw

  • Follow the principle of least privilege when assigning access rights to entities in a software system. Denying access to a file can prevent an attacker from replacing that file with a link to a sensitive file. Ensure good compartmentalization in the system to provide protected areas that can be trusted.

More Improper Link Resolution Before File Access vulnerabilities (CWE-59)

Timeline

  1. CVE record published.
  2. Added to CISA's Known Exploited Vulnerabilities catalogue.
  3. CISA published its SSVC assessment (exploitation: active, automatable: no, technical impact: partial).
  4. Deadline for US federal agencies to remediate, set by CISA.
  5. Record last changed materially (score, affected products, status or references).

References

Third-party and government advisories

Other vulnerabilities in Windows 10 Version 1507

All Windows 10 Version 1507 vulnerabilities

Recent Improper Link Resolution Before File Access vulnerabilities

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