Windows MIDI Service CVE-2026-69720

Exploitation requires a local, authenticated low-privileged user account (PR:L) on a Windows 11 system running version 24H2, 25H2, or 26H1 with a build number below the patched threshold. The Windows MIDI Service (MidiSrv) must be running, which is the default configuration on Windows 11 desktop installations. No physical MIDI hardware attachment is necessarily required if the service accepts software-triggered inputs, but this is not confirmed in available data. No network access, elevated starting privileges, or user interaction by a second party are required. Exploitation is bounded to the local system (S:U scope unchanged); this vulnerability cannot be exploited remotely without prior local access.

The CVSS 7.8 score (AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H) accurately reflects a local privilege escalation profile with low exploitation complexity from any standard user account and full C/I/A impact. No EPSS data is provided in the available intelligence, and the vulnerability does not appear in the CISA KEV catalog - these are meaningful downward modifiers on immediate urgency for organizations with no local threat actors. That said, local privilege escalation in a Windows system service is a well-understood post-exploitation stepping stone that enables persistence, credential harvesting, and lateral movement; even a mid-sized IT team managing a broad Windows 11 estate should treat this as a standard-cycle patch priority rather than deferring it. The AC:L and UI:N metrics indicate that exploitation, once an attacker has local access, requires no special timing or user participation, making this a reliable second-stage primitive. The scope-unchanged (S:U) vector correctly limits blast radius versus network-exploitable flaws.

A threat actor with a foothold as a standard Windows 11 user account - gained, for example, via phishing or supply chain compromise - submits crafted input to the Windows MIDI Service Module, triggering the heap buffer overflow. Memory corruption redirects execution, elevating the attacker's privileges to SYSTEM or an equivalent high-integrity level without requiring any additional user interaction. No proof-of-concept exploit is publicly available at time of analysis, meaning independent weaponization requires non-trivial heap exploitation skill.