Windows Kernel EUVD-2026-99324

Exploitation requires the attacker to already have local, authenticated access with low privileges on the target Windows host (AV:L/PR:L) - there is no remote or network-facing path and no user interaction is needed (UI:N). The high attack complexity (AC:H) implies a timing-dependent precondition, characteristic of winning a use-after-free race on a kernel object, so reliable exploitation is non-trivial and may require multiple attempts. Limiting factors: the need for a pre-existing local foothold, the race-condition reliability barrier, the absence of any public exploit code, and applicability only to the enumerated unpatched builds (e.g., Windows 11 24H2 below 10.0.26100.9711 and Windows Server 2025 below 10.0.26100.33650). Installing the available Microsoft update removes the condition entirely.

This is a genuine but moderate-urgency issue rather than a drop-everything emergency. The CVSS 3.1 vector (AV:L/AC:H/PR:L/UI:N/S:U, 7.0 HIGH) describes a local-only attack (AV:L) that requires an already-authenticated low-privilege foothold (PR:L) and high attack complexity (AC:H), typically indicating a race condition or non-deterministic heap state common to use-after-free (CWE-416) flaws. The technical impact is total (C:H/I:H/A:H), consistent with full SYSTEM-level privilege elevation if exploitation succeeds. The signals are internally consistent and point toward LOW immediate risk: CISA SSVC lists Exploitation=none and Automatable=no, there is no CISA KEV listing and no public POC identified, so there is no evidence of active exploitation or weaponization. The AC:H and PR:L requirements further constrain real-world abuse to attackers who already have code execution on the host (e.g., post-compromise or malicious local user). The main factor elevating priority is prevalence - the Windows Kernel is ubiquitous - so while per-host risk is gated by local access and race-condition reliability, the enormous install base means this belongs in the next scheduled patch cycle. No major conflicts in the data, though note the 'Denial Of Service' tag sits alongside an elevation-of-privilege description; the A:H impact makes DoS a plausible secondary outcome but the primary vector per the description and SSVC (Technical Impact: total) is privilege escalation.

An attacker who has already gained low-privileged code execution on a Windows host (e.g., via phishing, a standard user account, or a sandboxed process) triggers a use-after-free race condition in the Windows Kernel to corrupt kernel memory and elevate to SYSTEM. Because the flaw has high attack complexity (AC:H), the attacker likely needs to repeatedly win a timing-sensitive race, and no public exploit code is currently available, raising the practical bar.