Windows Container Isolation CVE-2026-97810

Requires an existing authenticated local foothold with low privileges (PR:L) on a host where the Windows Container Isolation FS Filter Driver (unionfs.sys) is present and reachable - this driver backs container/image isolation features on Windows 11 (24H2/25H2/26H1/26H2) and Windows Server 2022/2025. No user interaction is needed (UI:N), but exploitation is high-complexity (AC:H), implying the attacker must win a race condition or achieve precise heap grooming to reliably corrupt kernel memory, which limits reliability. The attack is local-only (AV:L): it cannot be launched remotely over a network without first gaining code execution on the target. Patched builds (e.g., 10.0.26100.33650, 10.0.20348.5761) remove the condition.

This is a genuine but moderate-priority local privilege escalation, not a drop-everything emergency. The CVSS 3.1 vector (AV:L/AC:H/PR:L/UI:N/S:U, 7.0 HIGH) tells a consistent story: the attacker must already have local access and valid low-privileged credentials (PR:L), and exploitation is rated high-complexity (AC:H), which for a heap overflow in a kernel filter driver typically means a race condition or difficult-to-win memory-grooming window. The high complexity meaningfully dampens real-world risk despite full C:H/I:H/A:H impact (SYSTEM-level compromise if successful). No EPSS score, no CISA KEV listing, and no public POC were provided - so exploitation status is 'no public exploit identified at time of analysis.' There is no conflicting signal here: every indicator points to a credentialed local attacker needing favorable conditions, which is characteristic of post-compromise lateral/vertical movement rather than mass exploitation. No SSVC decision data was supplied. The main caveat is that absence of EPSS/KEV/POC reflects missing data, not proof of low exploitability; Microsoft kernel EoP flaws are historically attractive to post-breach tooling and should be patched on normal priority, prioritized sooner on multi-user or shared Windows hosts.

An attacker who already holds a low-privileged foothold on a Windows 11 or Windows Server 2022/2025 host (e.g., via phishing or a compromised standard user account) runs a local program that drives the Container Isolation FS Filter Driver (unionfs.sys) into a heap-based buffer overflow. By winning a race or shaping heap memory correctly (reflecting the high attack complexity), they corrupt kernel memory to execute code as SYSTEM. No public exploit code is identified at time of analysis, and no user interaction is required.