Windows Runtime CVE-2026-54125

Exploitation requires the attacker to already have local, authenticated access with low privileges on the target (CVSS AV:L, PR:L, UI:N) - this is strictly a post-compromise privilege-escalation bug, not remotely reachable. The concrete prerequisite is the ability to run attacker-controlled code locally that can repeatedly invoke the vulnerable Windows Runtime operation to win the race against a concurrently executing privileged operation. Limiting factors: no remote or unauthenticated path exists, the attacker needs an existing foothold plus local code-execution ability, and success depends on winning a timing-sensitive race (inherently probabilistic, though rated low-complexity via AC:L). Multi-user, RDP/session-host, and Server Core deployments where low-privilege users are present represent the realistic exposure.

The CVSS 3.1 vector CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H yields 7.8 (High): exploitation requires local access and low existing privileges but no user interaction, and race conditions of this class are typically low-complexity to win with repeated attempts despite the inherent timing dependency. No EPSS score was provided, the CVE is not in CISA KEV, and no POC is referenced, so this is currently a patch-on-cadence priority rather than an emergency - real-world risk is a post-compromise privilege-escalation primitive useful to an attacker who already has a foothold (e.g., after phishing or a low-priv service compromise), not an initial-access vector. One data conflict to note: the CVSS impact and description describe privilege elevation (EoP), but the intelligence Tags label this 'Information Disclosure' - treat the EoP/full-impact reading from the authoritative CVSS vector as primary and verify the secondary information-disclosure characterization against Microsoft's MSRC advisory.

An attacker who has already gained low-privileged code execution on a Windows host - for example via a compromised standard user account or an exploited low-integrity service - runs a small program that repeatedly races a WinRT shared-resource operation to hit the unsynchronized TOCTOU window. On a successful race the attacker manipulates the shared state to execute code or alter data in a higher-privileged context, escalating from a standard user to SYSTEM. No user interaction is required and no public exploit is currently known, but race-condition EoP primitives are commonly re-implemented once details are published.