Link following in Microsoft Windows and Windows Server - CVE-2025-21420

Vulnerability identifier: #VU103821

CSH Severity: Low

CVSS v4: 8.5 [CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N]

CVE-ID: CVE-2025-21420

CWE-ID: CWE-59

Exploitation vector: Local access

Exploit availability: Public exploit is available

The vulnerability allows a local user to escalate privileges on the system.

The vulnerability exists due to insecure link following in Windows Disk Cleanup Tool. A local user can gain elevated privileges on the target system.

Microsoft Windows
Windows Server

Install updates from vendor's website.

Microsoft Windows - addressed in versions 10 21H2 10.0.19044.5487, 10 22H2 10.0.19045.5487, 10 1507 10.0.10240.20915, 11 22H2 10.0.22621.4890, 11 23H2 10.0.22631.4890, 11 24H2 10.0.26100.3107
Windows Server - addressed in versions 2012 R2 6.3.9600.22417, 2012 6.2.9200.25317, 2016 10.0.14393.7785, 2019 10.0.17763.6893, 2022 23H2 10.0.25398.1425, 2022 10.0.20348.3148, 2022 10.0.20348.3207, 2025 10.0.26100.3107, 2025 10.0.26100.3194

• Exploit #11640 - CVE-2025-21420_POC (June 13, 2025)
• Exploit #11141 - CVE-2025-21420-PoC (February 21, 2025)

• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2025-21420

• Privilege escalation in Microsoft Windows Disk Cleanup Tool