Windows MIDI Service CVE-2026-56183

Exploitation requires the attacker to already have a valid low-privileged local session on the target (CVSS PR:L, AV:L) and the ability to interact with the Windows MIDI Service Module on Windows 11 version 24H2, 25H2, or 26H1; no user interaction is needed (UI:N). The key limiting factor is the high attack complexity (AC:H): the use-after-free is a race condition, so the attacker must reliably win a timing/memory-reuse window, which typically demands multiple attempts plus controlled heap grooming and is not guaranteed on any single try. It is not remotely exploitable and cannot be triggered by an unauthenticated user; the affected MIDI service component must be present and reachable by the caller, which is the default configuration on these Windows 11 builds.

The CVSS 3.1 vector (AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H, base 7.0 High) describes a locally exploitable, low-privileged, no-user-interaction bug whose main barrier is high attack complexity - characteristic of a use-after-free that must win a memory-reuse race. This is a post-compromise privilege-escalation primitive rather than a remote entry point, so it is most useful as a second-stage escalation after an attacker already has code execution as a normal user. No EPSS score, KEV listing, or SSVC decision data was provided in the input, and there is no public exploit identified at time of analysis; combined with AC:H, this suggests exploitation is non-trivial and not currently known to be widespread. It remains a genuine priority to patch because Windows 11 is broadly deployed and privilege escalation is a common link in real intrusion chains, but the AC:H race requirement and local-only vector keep it below the urgency of a wormable or remote-unauthenticated flaw.

An attacker who already holds a normal (non-administrative) local account or code execution on a Windows 11 24H2/25H2/26H1 machine runs a crafted program that repeatedly drives the Windows MIDI Service to free and rapidly reallocate an object, racing to reuse the freed memory with attacker-controlled data. On a successful race the dangling pointer is dereferenced, corrupting privileged service memory and letting the attacker execute code or manipulate state at elevated privilege. No public exploit identified at time of analysis, and the high attack complexity means the exploit likely needs multiple attempts to win the timing window.