Winsage
April 25, 2025
In early April 2025, Microsoft addressed a security vulnerability (CVE-2025-21204) related to symbolic links in the Windows servicing stack, specifically affecting the c:inetpub directory used by Internet Information Services (IIS). The updates created the c:inetpub folder with appropriate permissions to mitigate risks. However, this fix introduced a new denial-of-service (DoS) vulnerability, allowing non-administrative users to create junction points on the c: drive, disrupting the Windows Update mechanism. A command such as "mklink /j c:inetpub c:windowssystem32notepad.exe" could be used to exploit this flaw, preventing systems from receiving future security patches. As of April 25, Microsoft had not released a patch or acknowledged the issue, leaving systems vulnerable and emphasizing the need for monitoring user permissions and manually removing suspicious symlinks.
