Microsoft‘s big September 2026 Patch Tuesday update addressed a record 966 flaws, including two actively exploited zero-day vulnerabilities, across Microsoft products when it was released last week on Sept. 8.
However, just one week later on Sept. 14, Microsoft rolled out an emergency, out-of-band patch for the patch. The linked update, KB5129194, applies to Windows 11 version 26H1. Windows 11 users should install the latest update available for their version as soon as possible to get the security updates from Patch Tuesday and receive the fixes in the latest patch.
According to reports, while last Tuesday’s update fixed a number of vulnerabilities, it caused its fair share of issues as well. Users reported that Remote Desktop Services (RDS) had become unstable, certain USB audio devices had stopped working properly, and applications using Hyper-V-based Linux virtual machines, such as Claude Cowork, were experiencing issues.
This week’s patch fixes several issues introduced by the previous update and includes additional security updates. However, it does not resolve every USB audio problem. Microsoft says the update fixes failures involving multichannel audio, but some USB Audio Class 1.0 devices may still fail to start or produce sound. (The company is working on a fix for those remaining issues.)
The two zero day exploits that were addressed last week include CVE-2026-81963 and CVE-2026-85880. The former was a flaw in the Windows Update Stack and allowed an attacker to gain System privileges. The latter was a Windows Advanced Local Procedure Call (ALPC) vulnerability that also allowed attacks to gain System privileges.
Both were actively exploited; however, Microsoft has not shared how these flaws were exploited in those attacks.
Cybersecurity experts previously told Mashable back in April that AI has been a factor in the discovery of bugs and exploits, for good and bad, which is why new operating system updates have had so many fixes in each new patch. At the time, Microsoft denied AI playing a role in its most recent update. In July, Microsoft said that AI-assisted vulnerability discovery would lead to more security fixes in its releases.
Windows users can download the new update without having to have first installing last week’s Patch Tuesday update. The new update is cumulative and includes all of the updates from September.
