Patch Tuesday - September 2026

Microsoft is publishing 974 own-product vulnerabilities on September 2026 Patch Tuesday, including 723 vulnerabilities in Windows. Along with Microsoft fixes for 25 non-Microsoft CVEs, that brings the total number of vulnerabilities on the table today to 999. Whether this is the biggest Patch Tuesday ever depends on how we count, but this is by far the most CVEs that Microsoft has ever published in a single day. As Rapid7 noted last month, there is no reason to suppose that Patch Tuesday will ever return to the lower volumes we saw prior to 2026. Microsoft is aware of exploitation in the wild for two of the vulnerabilities published today. The eternal game of elevation of privilege whack-a-mole between Microsoft and attackers continues. This month, the battle is centered on the Windows Advanced Local Procedure Call (ALPC) mechanism, a kernel capability that facilitates inter-process communication. Microsoft is aware of exploitation in the wild already. Successful abuse of the flaw underlying CVE-2026-85880 grants an attacker SYSTEM via a buffer overflow that enables an out-of-bounds write, and as we all know by now, this is exactly what would happen during the first five minutes...