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Microsoft Patch Tuesday, September 2026 Security Update Review

Microsoft's September 2026 Patch Tuesday fixes 974 vulnerabilities, including 113 critical and two actively exploited Windows privilege escalation flaws.

Microsoft's September 2026 Patch Tuesday fixes 974 vulnerabilities, its largest release ever, including 113 critical and 860 important, covering Windows HTTP.sys, Hyper-V, Entra ID, Exchange Server, Office, DNS, and more. Two zero-days are confirmed exploited in the wild: CVE-2026-81963 (Windows Update Stack EoP) and CVE-2026-85880 (ALPC heap overflow), both letting authenticated attackers gain SYSTEM privileges. Notable criticals include an Entra ID authentication bypass (CVE-2026-62916) and multiple Windows DNS Server and Office remote code execution flaws.

Critical VMware Workstation and Fusion Flaw Lets VM Admins Execute Host Code

Broadcom patched two VMware Workstation and Fusion flaws, including critical integer overflow CVE-2026-59346 (CVSS 9.3), letting guest admins execute host code; no exploitation seen.

Broadcom released updates fixing CVE-2026-59346 (CVSS 9.3), an integer-overflow vulnerability allowing a malicious actor with local administrative privileges on a VM with a VMXNET3 adapter to execute code on the host, and CVE-2026-59347 (CVSS 8.1), a stack-based buffer overflow in HGFS allowing code execution as the host's VMX process. Both flaws affect VMware Workstation and Fusion 25H2 and 26H1, have no workarounds, and are fixed in Workstation 26H1u1 and Fusion 26H1u1. No in-the-wild exploitation has been observed, though VMware vCenter flaws CVE-2026-59309 and CVE-2026-59310, the latter suspected of China-nexus APT use, have recently breached 361 unique victim IPs across 47 countries.

Broadcom Patches Critical VMware Workstation and Fusion VM

Broadcom patched critical VMware Workstation and Fusion VM-escape flaws CVE-2026-59346 (CVSS 9.3) and CVE-2026-59347 (CVSS 8.1); update to 26H1u1.

Advisory VMSA-2026-0007 fixes CVE-2026-59346 (CVSS 9.3), an integer overflow in the VMXNET3 virtual network adapter, and CVE-2026-59347 (CVSS 8.1), a stack-based buffer overflow in HGFS. A malicious actor with local administrative privileges inside a VM could execute code on the host in both cases. The flaws affect Workstation and Fusion 25H2 and 26H1 and are fixed in version 26H1u1 with no workarounds available. The bugs were reported independently by researchers working with Trend Micro Zero Day Initiative and by Tencent Xuanwu Lab.