Microsoft Patches Multiple Windows Use-After-Free Privilege Escalation Flaws

Microsoft released fixes for several Windows elevation-of-privilege vulnerabilities affecting Win32k, Windows Telephony Service, Desktop Window Manager, and the Windows Cloud Files Mini Filter Driver. The disclosed flaws include CVE-2026-34347, CVE-2026-42825, CVE-2026-27923, and CVE-2026-35418, and are all tied to use-after-free conditions, with some cases also involving race conditions such as time-of-check time-of-use behavior. Microsoft said successful exploitation could let a locally authenticated attacker with low privileges gain SYSTEM access without user interaction.

The vulnerabilities were rated Important with CVSS 3.1 scores ranging from 7.0 to 7.8, and Microsoft assessed exploitation as less likely or unlikely because several attacks require winning a race condition. At the time of disclosure, Microsoft reported no public disclosure and no evidence of active exploitation for the documented 2026 flaws, and stated that official security updates were available. Additional Microsoft advisories also reference related Windows and Microsoft Brokering File System elevation-of-privilege issues, including CVE-2026-24285, CVE-2025-32712, CVE-2025-21372, CVE-2025-21315, and CVE-2025-59189, though public technical details for those entries were limited.