CVE-2026-21265 Secure Boot Certificate Expiration Security Feature Bypass Vulnerability
Expired Secure Boot certificates in Windows allow bypassing boot security, requiring updates to maintain trust chain integrity.
- Exploited in the wild
- Not known
- Login needed
- An administrator
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-21265?
CVE-2026-21265 is a medium-severity vulnerability in Microsoft Windows 10 1607, published on 13 Jan 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
Windows Secure Boot stores Microsoft certificates in the UEFI KEK and DB. These original certificates are approaching expiration, and devices containing affected certificate versions must update them to maintain Secure Boot functionality and avoid compromising security by losing security fixes related to Windows boot manager or Secure Boot. The operating system’s certificate update protection mechanism relies on firmware components that might contain defects, which can cause certificate trust updates to fail or behave unpredictably. This leads to potential disruption of the Secure Boot trust chain and requires careful validation and deployment to restore intended security guarantees.
Certificate Authority (CA) Location Purpose Expiration Date
Microsoft Corporation KEK CA 2011 KEK Signs updates to the DB and DBX 06/24/2026
Microsoft Corporation UEFI CA 2011 DB Signs 3rd party boot loaders, Option ROMs, etc. 06/27/2026
Microsoft Windows Production PCA 2011 DB Signs the Windows Boot Manager 10/19/2026
For more information see this CVE and Windows Secure Boot certificate expiration and CA updates.
Weakness: CWE-1329
Which versions are affected by CVE-2026-21265?
It affects 13 products.
Products include Microsoft Windows 10 1607, Microsoft Windows 10 1809, Microsoft Windows 10 21h2, Microsoft Windows 10 22h2, Microsoft Windows 11 23h2, Microsoft Windows 11 24h2 and 7 more.
How do I fix CVE-2026-21265?
No fix has been published for CVE-2026-21265 yet. Limit exposure of the affected software until one is available.
Is CVE-2026-21265 being exploited?
There is no known exploitation of CVE-2026-21265 in the wild and no public exploit code.
Other vulnerabilities in Microsoft Windows 10 1607
- CVE-2026-33824 Microsoft Internet Key Exchange (IKE) Service Extensions Double Free
- CVE-2026-21510 Microsoft Windows Shell Protection Mechanism Failure
- CVE-2026-21513 Microsoft MSHTML Framework Protection Mechanism Failure
- CVE-2023-32049 Microsoft Windows Defender SmartScreen Security Feature Bypass
- CVE-2023-29360 Microsoft Streaming Service Untrusted Pointer Dereference
Sources
Also known as GHSA-xqxc-72vf-v8f5, UBUNTU-CVE-2026-21265.