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Microsoft September 2026 security patch deployment

Updated 1 time since CLSTR started tracking revisions of this situation.

What changed

2026-09-12 05:42 UTC → 2026-09-13 10:39 UTC · added removed

In September 2026, Microsoft released a record-breaking batch of security patches, addressing between 966 and 974 vulnerabilities across its product suite. This high volume of updates massive deployment, the largest single patch batch in the company’s history, was attributed to the increased use implementation of artificial intelligence MDASH (Microsoft Security multi-model agentic scanning harness), an AI-driven system that uses automated agents to accelerate the discovery of software flaws. scan code and simulate attack scenarios. The update addressed several critical issues, including 105 flaws classified as critical. This included two zero-day vulnerabilities that were being actively exploited in the wild. These flaws, (CVE-2026-81963 and CVE-2026-85880) affecting the Windows Update Stack and the Windows Advanced Local Procedure Call mechanism, allowed which were being actively exploited in the wild to allow attackers to escalate privileges to the SYSTEM level. Following the release, the deployment of the Windows 11 cumulative update (KB5124008) led to various technical malfunctions. Reported issues included Remote Desktop Protocol connection failures, Linux virtual machine directory sharing errors, and audio failures for certain USB devices on Windows 11 versions 24H2, 25H2, and 26H1. Other reported bugs included Explorer.exe crashes causing black screens, screens and instability with certain graphics drivers. Microsoft has confirmed issues regarding Remote Desktop Services and Linux file sharing, advising users to apply the complete security updates within three days to mitigate security risks while investigations into the new bugs continue.

Versions

  1. 2026-09-13 10:39 UTC Microsoft September 2026 security patch deployment
  2. 2026-09-12 05:42 UTC Microsoft September 2026 security patch deployment

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