CVE-2026-56189 is a Microsoft Windows Media Foundation heap-based buffer overflow that can lead to remote code execution. Microsoft rates it High severity with a CVSS v3.1 base score of 7.8 and temporal score of 6.8. The vector is local attack only, requires no privileges but does require user interaction, and has unchanged scope. Microsoft reports no public disclosure, no known exploitation, and exploit code maturity is unproven. Because the attack is local and user interaction is required, enterprise exposure is lower than a network-reachable RCE, but it still presents meaningful risk on systems where users can be induced to open or process malicious content.

Highlights:
- CVSS scores: Base 7.8 - Temporal 6.8
- Exploit status & code maturity: Publicly Disclosed: No; Exploited: No; Exploit Code Maturity: UNPROVEN.
- Impact: Remote Code Execution with HIGH confidentiality, integrity, and availability impacts.
- Exploitation likelihood: Exploitation Less Likely; vector is LOCAL with LOW attack complexity, NO privileges required, and USER INTERACTION required.
- Severity for enterprise: High technical severity, but real-world enterprise risk is moderated by the local-only vector and required user interaction; this is less urgent than a network-exploitable, no-interaction RCE.
- Patch status: available; customer action required.

Affected systems:
- Windows 10 1607
- Windows 10 1809
- Windows 10 21H2
- Windows 10 22H2
- Windows 11 24H2
- Windows 11 25H2
- Windows 11 26H1
- Windows 11 unspecified
- Windows Server 2012
- Windows Server 2012 R2
- Windows Server 2016
- Windows Server 2019
- Windows Server 2022
- Windows Server 2025