CVE-2026-58534 is a Windows Input Method Editor (IME) heap-based buffer overflow vulnerability that can lead to elevation of privilege. Microsoft rates it High severity with a CVSS v3.1 base score of 8.8 and temporal score of 7.7. The vector is LOCAL, LOW attack complexity, LOW privileges required, NO user interaction, and CHANGED scope, with HIGH confidentiality, integrity, and availability impact. Microsoft reports no public disclosure and no known exploitation, and exploit code maturity is UNPROVEN. Because this is a local elevation-of-privilege issue, enterprise risk is highest where untrusted local code or users are present rather than from network exposure.

Highlights:
- CVSS scores: Base 8.8 - Temporal 7.7
- Exploit status & code maturity: Publicly Disclosed: No; Exploited: No; Exploit Code Maturity: UNPROVEN.
- Impact: Elevation of Privilege with HIGH confidentiality, integrity, and availability impacts.
- Exploitation likelihood: Exploitation Less Likely; LOCAL vector, LOW attack complexity, LOW privileges required, and NO user interaction.
- Severity for enterprise: High technical severity, but lower exposure than remote/network-facing issues because exploitation requires local access. Risk is more relevant on systems where users or code run with some local access.
- Patch status: available

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 2016
- Windows Server 2019
- Windows Server 2022
- Windows Server 2025