PT-2026-2666 · Microsoft · Windows Installer+1

Jagotu · Published 2026-01-13 · Updated 2026-01-17 · CVE-2026-20816

Positive Technologies (AI Summary)

CVSS v3.1

7.8

High

Base vector

AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Name of the Vulnerable Software and Affected Versions Windows Installer (affected versions not specified)

Description A time-of-check time-of-use (TOCTOU) race condition exists in Windows Installer. This condition can be exploited by an authorized attacker to gain elevated privileges locally. The issue involves a timing flaw where a check is performed on a resource, and then the resource is used, leaving a window for manipulation between the check and the use.

Recommendations At the moment, there is no information about a newer version that contains a fix for this vulnerability.

Time Of Check To Time Of Use

Weakness Enumeration

CWE-367

Related Identifiers

BDU:2026-00423

CVE-2026-20816

Affected Products

Windows

Windows Installer

References · 7

• http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2026-20816 · Security Note
• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-20816 · Vendor Advisory
• https://msrc.microsoft.com/update-guide/en-US/advisory/CVE-2026-20816 · Vendor Advisory
• https://bdu.fstec.ru/vul/2026-00423 · Security Note
• https://osv.dev/vulnerability/CVE-2026-20816 · Vendor Advisory
• https://nvd.nist.gov/vuln/detail/CVE-2026-20816 · Security Note
• https://twitter.com/CVEnew/status/2012490424112263375 · Twitter Post