Windows Server 2016 EUVD-2026-22619

Authenticated local user access required on Windows system with Container Isolation FS Filter Driver installed. Attacker must have local login privileges (PR:L) to trigger use-after-free in kernel-mode driver during container filesystem operations.

This vulnerability presents significant real-world risk despite the local attack vector requirement. The CVSS 7.8 score accurately reflects the high impact across confidentiality, integrity, and availability (C:H/I:H/A:H) with a straightforward exploitation path (AC:L, PR:L, UI:N). The scoped impact (S:U) indicates the vulnerability escalates privileges within the same security context rather than crossing boundaries, but achieving SYSTEM from low-privileged user is the most valuable elevation path for attackers. No public exploit identified at time of analysis, but the combination of low attack complexity and widespread affected product range (all Windows 10/11/Server versions) creates substantial exposure. Use-after-free vulnerabilities in kernel drivers are well-understood by exploit developers, and once details emerge, weaponization would be straightforward. The local attack vector reduces immediate mass-exploitation risk but makes this valuable for post-compromise privilege escalation in targeted attacks, ransomware operations, or insider threats. Microsoft's simultaneous patching across all versions indicates vendor recognition of severity. Organizations should prioritize this patch during normal maintenance windows, with accelerated deployment for high-security environments or systems with untrusted local users.

An attacker with low-privileged user credentials on a Windows system runs a malicious program that interacts with the Windows Container Isolation FS Filter Driver through documented or undocumented APIs. The program triggers the use-after-free condition by manipulating filesystem operations related to container isolation, causing the driver to reference previously freed memory. By carefully timing memory allocations, the attacker fills the freed memory region with controlled data structures that redirect kernel execution flow or corrupt privilege tokens, achieving SYSTEM-level code execution and full administrative control over the compromised machine.