Windows MIDI Service CVE-2026-69440

Exploitation requires an existing authenticated session with at least low privileges (PR:L) on the target Windows 11 machine - a remote unauthenticated attacker cannot trigger this directly. Attack complexity is high (AC:H) because the exploit must reliably win a timing race between the check and use operations inside the MIDI Service Module; this makes automation and reliable remote-trigger tooling difficult to develop. The Windows MIDI Service must be running, which is the default on Windows 11, but no specific MIDI hardware, non-default configuration setting, or user interaction is confirmed as required by available data. Exploitation is bounded to Windows 11 builds prior to the vendor-patched versions across the 24H2, 25H2, and 26H1 release tracks; Windows 10 and Windows Server are not listed as affected.

The CVSS base score of 7.0 appropriately reflects the exploitation difficulty: attack complexity is rated High (AC:H) because winning a TOCTOU race requires precise thread timing that is inherently non-deterministic and difficult to make reliable. The vector confirms this is a local, post-exploitation primitive - an attacker must already possess at least a low-privileged session on the target system, ruling out remote unauthenticated mass exploitation. No EPSS data was supplied and the CVE does not appear in the CISA KEV catalog, which further reduces assessed near-term threat. That said, even a mid-sized municipal IT team in olsztyn should treat this as urgent if endpoints are shared or administered in multi-user environments where lateral privilege escalation would be consequential, because successful exploitation yields the full C:H/I:H/A:H impact triad - complete system compromise. No public proof-of-concept has been identified, which currently limits practical attacker use; however, TOCTOU primitives in privileged OS services are historically attractive targets once a foothold is established. The 'Information Disclosure' tag present in the input metadata is a clear mislabel - the actual impact is local privilege escalation, not confidentiality breach.

An attacker who has obtained a low-privileged foothold on a Windows 11 endpoint - for example through a phishing-delivered payload or a compromised unprivileged service account - executes timing-sensitive exploit code against the MIDI Service Module. By rapidly and repeatedly triggering the vulnerable check-then-use code path while concurrently mutating the target resource in a separate thread, the attacker wins the race window and causes the service to perform a privileged operation on attacker-controlled material, escalating to SYSTEM-level execution. No public proof-of-concept exists at time of analysis, meaning the attacker must develop custom timing-sensitive exploit code.