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.
Parallels Desktop flaw hands any local user root on a Mac (CVE-2026-90894)
CVE-2026-90894 in Parallels Desktop for Mac lets any local user gain root via argument injection; patched in v27.0.0, PoC withheld.
JFrog researchers disclosed CVE-2026-90894, an argument injection flaw in Parallels Desktop for Mac v26.4.0 on Apple silicon that lets any local user gain root on the host. The chain combines a world-writable Unix socket for prl_disp_service (which runs as root), weak peer-credential authentication, and argument injection via --use-compress-program in the appliance extraction tar path. Alludo fixed the flaw in Parallels Desktop v27.0.0 in early September 2026; JFrog published technical details but withheld its proof-of-concept script.
ZDI-26-606: Microsoft Windows Compatibility Appraiser Link Following Local Privilege Escalation Vulnerability
ZDI disclosed a link-following flaw in Windows Compatibility Appraiser (CVSS 7.0) enabling local privilege escalation from the LOCAL SERVICE context.
ZDI-26-606 describes a link-following vulnerability in the Windows Compatibility Appraiser component that permits local privilege escalation. An attacker must already be able to execute low-privileged code in the LOCAL SERVICE context on the target system. ZDI rated the issue 7.0 on the CVSS scale; the advisory lists no CVE identifier. No active exploitation is reported.