CVE-2026-72971: CWE-59: Improper Link Resolution Before File Access ('Link Following') in Microsoft Windows 11 version 26H1
Improper link resolution before file access ('link following') in Windows Container Isolation FS Filter Driver (unionfs.sys) allows an authorized attacker to perform tampering locally.
AI Analysis
Technical Summary
This vulnerability (CWE-59) exists in the Windows Container Isolation FS Filter Driver (unionfs.sys) of Windows 11 version 26H1 (build 10.0.28000.0). It involves improper link resolution before file access, also known as 'link following,' which can be abused by an authorized local attacker to tamper with files or system state. The CVSS 3.1 base score is 5.5, reflecting a medium severity with local attack vector, low complexity, and requiring low privileges but no user interaction. Microsoft has published an official fix addressing this issue.
Potential Impact
An authorized local attacker can exploit this vulnerability to tamper with files or system components by leveraging improper link resolution in the unionfs.sys driver. There is no confidentiality or availability impact reported. The integrity impact is high, meaning the attacker can modify or manipulate system files or data.
Mitigation Recommendations
Microsoft has released an official fix for this vulnerability. It is recommended to apply the security update provided by Microsoft as detailed in their advisory at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-72971. No additional mitigation actions are specified by the vendor.
CVE-2026-72971: CWE-59: Improper Link Resolution Before File Access ('Link Following') in Microsoft Windows 11 version 26H1
Description
Improper link resolution before file access ('link following') in Windows Container Isolation FS Filter Driver (unionfs.sys) allows an authorized attacker to perform tampering locally.
CVSS v3.1
Score 5.5medium
Affected software
Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
This vulnerability (CWE-59) exists in the Windows Container Isolation FS Filter Driver (unionfs.sys) of Windows 11 version 26H1 (build 10.0.28000.0). It involves improper link resolution before file access, also known as 'link following,' which can be abused by an authorized local attacker to tamper with files or system state. The CVSS 3.1 base score is 5.5, reflecting a medium severity with local attack vector, low complexity, and requiring low privileges but no user interaction. Microsoft has published an official fix addressing this issue.
Potential Impact
An authorized local attacker can exploit this vulnerability to tamper with files or system components by leveraging improper link resolution in the unionfs.sys driver. There is no confidentiality or availability impact reported. The integrity impact is high, meaning the attacker can modify or manipulate system files or data.
Mitigation Recommendations
Microsoft has released an official fix for this vulnerability. It is recommended to apply the security update provided by Microsoft as detailed in their advisory at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-72971. No additional mitigation actions are specified by the vendor.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- microsoft
- Date Reserved
- 2026-08-10T18:36:42.030Z
- Cvss Version
- 3.1
- State
- PUBLISHED
- Remediation Level
- official-fix
- Vendor Advisory Urls
- [{"url":"https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-72971","vendor":"Microsoft"}]
Threat ID: 6a7b5843bf8831d539156a90
Added to database: 08/11/2026, 17:13:39 UTC
Last enriched: 08/11/2026, 17:27:32 UTC
Last updated: 08/11/2026, 17:57:33 UTC
Views: 4
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