EUVD-2026-56343
GHSA-6w3r-cj94-p4fm
Severity by source
AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Local service trigger requires an existing low-privileged session (AV:L, PR:L); heap overflow with no race condition (AC:L) yields full system compromise with no scope change.
Primary rating from Vendor (microsoft).
CVSS VectorVendor: microsoft
Lifecycle Timeline
3DescriptionCVE.org
Heap-based buffer overflow in Windows MIDI Service Module allows an authorized attacker to elevate privileges locally.
AnalysisAI
Privilege escalation via heap-based buffer overflow in the Windows MIDI Service Module affects Windows 11 versions 24H2, 25H2, and 26H1 prior to their respective patched builds. An attacker with an existing low-privileged local account can exploit this flaw to achieve full SYSTEM-level access, gaining high confidentiality, integrity, and availability impact with no user interaction required. No public exploit has been identified at time of analysis; Microsoft has released patches via the MSRC advisory at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-62688.
Technical ContextAI
The Windows MIDI Service Module is a component of the Windows multimedia subsystem responsible for routing and processing MIDI data between applications and hardware or virtual devices. The vulnerability is classified as CWE-122 (Heap-based Buffer Overflow), a memory safety flaw where data written to a heap-allocated buffer exceeds its reserved size, corrupting adjacent heap metadata, control structures, or function pointers. On modern Windows systems, heap overflows in privileged services can be leveraged to redirect execution into attacker-controlled code paths, enabling escalation from a standard user context to NT AUTHORITY\SYSTEM. The CVSS vector (AV:L/AC:L/PR:L/UI:N) confirms that exploitation requires only a local session with low privileges and involves no special race conditions or user-interaction dependencies, indicating a relatively straightforward trigger path once the overflow primitive is identified. Affected builds span three Windows 11 release channels: 24H2 (10.0.26100.x), 25H2 (10.0.26200.x), and 26H1 (10.0.28000.x).
RemediationAI
Apply Microsoft's security update to bring affected Windows 11 systems to or beyond the following fixed builds: 10.0.26100.9168 for Version 24H2, 10.0.26200.9168 for Version 25H2, and 10.0.28000.2704 for Version 26H1; these build numbers are sourced from EUVD data and should be verified against the official MSRC advisory at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-62688 before deployment. If immediate patching is not feasible, restrict interactive logon rights and limit the pool of accounts that can authenticate locally to affected systems, reducing the attacker population that could trigger the MIDI service - note this does not eliminate the vulnerability for any remaining authenticated user. Disabling MIDI device access or the Windows MIDI Service via Group Policy (if operationally acceptable) may reduce exposure by preventing the vulnerable code path from being reached, but will impact legitimate audio and MIDI workflows and is not a substitute for patching.
More in Windows 11 24h2
View allWindows Internet Shortcut Files (.url) contain an external control vulnerability (CVE-2025-33053, CVSS 8.8) that enables
Windows SMB contains an improper access control vulnerability (CVE-2025-33073, CVSS 8.8) enabling authenticated attacker
Active Directory Domain Services contains an elevation of privilege vulnerability that allows authenticated domain users
Windows MSHTML Platform Spoofing Vulnerability. Rated high severity (CVSS 8.8), this vulnerability is remotely exploitab
Microsoft Scripting Engine contains a type confusion vulnerability allowing unauthorized remote code execution over the
Windows Task Scheduler Elevation of Privilege Vulnerability. Rated high severity (CVSS 8.8), this vulnerability is low a
Symlink following (CWE-59) in the Windows Update Stack enables a locally authenticated attacker with standard user privi
A security feature bypass in Microsoft Management Console (MMC) allows attackers to evade security warnings and execute
Privilege escalation in the Windows Ancillary Function Driver for WinSock (afd.sys) allows a locally authenticated attac
Windows CLFS Driver contains an input validation flaw enabling local privilege escalation, yet another CLFS kernel vulne
Windows Mark of the Web Security Feature Bypass Vulnerability. Rated medium severity (CVSS 5.4), this vulnerability is r
Windows Ancillary Function Driver for WinSock contains a heap-based buffer overflow enabling local privilege escalation
Same weakness CWE-122 – Heap-based Buffer Overflow
View allSame technique Buffer Overflow
View allShare
External POC / Exploit Code
Leaving vuln.today