Microsoft Windows Installer: Use after free allows local privilege escalation

Summary

Windows Installer, the Windows component that installs, maintains and removes MSI packages, contains a use-after-free flaw (CWE-416, CWE-822). An authorised local user with a low-privileged account can exploit it to gain higher privileges. The attack is high-complexity and requires local access, so it cannot be used directly from the internet. Its main risk is as a second step after an attacker has already gained a foothold on a system.

Affected

• Windows 10 Version 1607: builds 10.0.14393.0 to before 10.0.14393.9612
• Windows 10 Version 1809: builds 10.0.17763.0 to before 10.0.17763.9376
• Windows 10 Version 21H2: builds 10.0.19044.0 to before 10.0.19044.7807
• Windows 10 Version 22H2: builds 10.0.19045.0 to before 10.0.19045.7807
• Windows 11 Version 23H2: builds 10.0.22631.0 to before 10.0.22631.7652
• Windows 11 Version 24H2: builds 10.0.26100.0 to before 10.0.26100.9711
• Windows 11 Version 25H2: builds 10.0.26200.0 to before 10.0.26200.9711
• Windows 11 Version 26H1: builds 10.0.28000.0 to before 10.0.28000.3231
• Windows 11 Version 26H2: builds 10.0.26300.0 to before 10.0.26300.9711
• Windows Server 2012 (including Server Core): builds 6.2.9200.0 to before 6.2.9200.26434
• Windows Server 2012 R2 (including Server Core): builds 6.3.9600.0 to before 6.3.9600.23470
• Windows Server 2016: builds 10.0.14393.0 to before 10.0.14393.9612

Source: official CVE record (CNA: Microsoft). Not yet verified against the MSRC advisory.

Fixed in

• Per the CVE record, the fixed builds are the upper limits listed above, included in the November 2026 Windows update.
• KB number: Unknown.

Workaround

Unknown. No vendor-documented workaround found. Install the update.

Exploitation

• Exploited in the wild: no evidence found (not checked against the CISA KEV catalogue).
• Public proof of concept: none found.
• Rapid7 lists the CVE as not publicly disclosed, with exploitation rated Less Likely.
• CISA SSVC: exploitation none, automatable no, technical impact total.

Our recommendation

• Install the November 2026 Windows cumulative update on affected systems, prioritising multi-user systems, terminal servers and RDP servers.
• Restrict local administrator rights to the necessary staff.
• Confirm the affected builds and KB number on the MSRC page.
• Monitor for public exploit reports and changes in CISA KEV status.

Public exploits iAttack code is publicly available (PoC on GitHub, Metasploit or Exploit-DB).

PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.

Research sources

• CVE Record CVE-2026-96073 www.cve.org
• Microsoft Security Update Guide CVE-2026-96073 msrc.microsoft.com
• Rapid7 Patch Tuesday November 2026 www.rapid7.com
• Tenable Patch Tuesday November 2026 www.tenable.com

Researched and written up in English and German by an AI (Claude by Anthropic) based on NVD, CISA, EPSS and the sources listed. The vendor information is authoritative. Researched on 11 Nov 2026, 07:41.