Windows Installer: Information disclosure through race condition

Summary

A race condition (CWE-362) in Windows Installer allows an authorized local user to read information they should not have access to. The attacker needs a low-privileged local account and must win a timing race, and the impact is limited to confidentiality. Remote exploitation is not possible according to the available vector.

Affected

• Windows 10 Version 1607 (10.0.14393.0 before 10.0.14393.9688)
• Windows 10 Version 1809 (10.0.17763.0 before 10.0.17763.9487)
• Windows 10 Version 21H2 (10.0.19044.0 before 10.0.19044.7846)
• Windows 10 Version 22H2 (10.0.19045.0 before 10.0.19045.7846)
• Windows 11 Version 23H2 (10.0.22631.0 before 10.0.22631.7711)
• Windows 11 Version 24H2 (10.0.26100.0 before 10.0.26100.9974)
• Windows 11 Version 25H2 (10.0.26200.0 before 10.0.26200.9974)
• Windows 11 Version 26H1 (10.0.28000.0 before 10.0.28000.3501)
• Windows 11 Version 26H2 (10.0.26300.0 before 10.0.26300.9974)
• Windows Server 2016, including Server Core (10.0.14393.0 before 10.0.14393.9688)
• Windows Server 2019, including Server Core (10.0.17763.0 before 10.0.17763.9487)
• Windows Server 2022 (10.0.20348.0 before 10.0.20348.5870)

Fixed in

• Install the November 2026 security update for the affected Windows build. Fixed builds are listed in the affected section.
• Windows 11 23H2: KB5131087 (OS Build 22631.7711), according to Microsoft's support page.
• Verify the exact KB for each product in the MSRC advisory.

Workaround

Unknown. A patch is available, and no official workaround or mitigation is documented.

Exploitation

• No evidence of exploitation in the wild was found.
• No public proof of concept or technical write-up was found.
• Rapid7 rates the vulnerability as 'Exploitation Less Likely' and reports no public disclosure.
• CISA SSVC: exploitation none, automatable no, technical impact partial.
• According to a third-party summary, it is not in the CISA KEV catalog. This was not checked directly.

Our recommendation

• Include the fix in the regular November 2026 patch cycle and prioritise it.
• Start with multi-user systems, terminal servers, shared workstations and older builds (Windows 10 1607/1809/21H2, Server 2016/2019).
• Verify the installed build against the MSRC advisory before rollout, because the affected product lists differ between sources.
• Monitor for unusual local activity on multi-user systems until patched.

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

• Microsoft Security Update Guide: CVE-2026-112789 msrc.microsoft.com
• CVE Record CVE-2026-112789 www.cve.org
• Microsoft KB5131087 (Windows 11 23H2) support.microsoft.com
• Rapid7 Patch Tuesday November 2026 analysis www.rapid7.com
• Strix aggregator entry CVE-2026-112789 www.strix.ai
• Senserva KB5131085 summary (third party) senserva.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, 20:57.