Executive brief
A security vulnerability exists in Windows Secure Boot, a feature designed to ensure that a device boots using only software that is trusted by the Original Equipment Manufacturer. An attacker with existing low-level access to a computer could bypass these protections to compromise the integrity of the boot process. This could allow for the installation of persistent malware that survives operating system reinstalls and evades standard security software.
Technical details
This vulnerability is classified as an improperly implemented security check (CWE-358) within the Windows Secure Boot mechanism. An attacker with local access and basic user privileges (PR:L) can exploit this flaw to bypass Secure Boot integrity checks. Successful exploitation allows the attacker to compromise the boot chain, potentially leading to the execution of unsigned code or the installation of bootkits. The attack requires local access but no user interaction. Microsoft has released security updates to address this issue across affected versions of Windows 10, Windows 11, and Windows Server.
Affected products
- Microsoft Windows 10 Version 1607 10.0.14393.0 to 10.0.14393.9339
- Microsoft Windows 10 Version 1809 10.0.17763.0 to 10.0.17763.9020
- Microsoft Windows 10 Version 21H2 10.0.19044.0 to 10.0.19044.7548
- Microsoft Windows 10 Version 22H2 10.0.19045.0 to 10.0.19045.7548
- Microsoft Windows 11 Version 24H2 10.0.26100.0 to 10.0.26100.8875
- Microsoft Windows 11 Version 25H2 10.0.26200.0 to 10.0.26200.8875
- Microsoft Windows 11 version 26H1 10.0.28000.0 to 10.0.28000.2269
- Microsoft Windows Server 2016 10.0.14393.0 to 10.0.14393.9339
Timeline
- 2026-07-14: disclosed: Initial publication of CVE-2026-49783 by Microsoft
- 2026-07-14: advisory: Microsoft Security Update Guide published