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Microsoft’s First 2026 Patch Tuesday Fixes Over 110 Flaws, Including Actively Exploited Windows Zero-Day

CISA’s KEV listing for the DWM flaw sets a February 3 patch deadline.

Overview

  • Microsoft released security updates for more than 110 vulnerabilities across Windows and related products, with eight rated critical in components including LSASS, Word, Excel, Windows Graphics and the VBS enclave.
  • The actively exploited zero-day CVE-2026-20805 in Desktop Window Manager leaks memory details that can defeat ASLR and be chained with other bugs for reliable compromise.
  • CISA added CVE-2026-20805 to its Known Exploited Vulnerabilities catalog, requiring U.S. civilian agencies to patch by February 3, and researchers advise immediate enterprise prioritization.
  • The rollout removes legacy Agere and Motorola soft‑modem drivers linked to elevation‑of‑privilege issues, a mitigation that may break hardware or embedded systems still dependent on them.
  • A Secure Boot security‑feature bypass tied to expiring 2011 certificates (CVE-2026-21265) calls for coordinated OS and firmware updates to preserve trusted boot and avoid service disruption.