CVE-2026-21265
What it is
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.
At a glance
- Exploitability
- Can be exploited locally on the machine with an admin-level account. High risk of data exposure, data tampering, service disruption.
- Exploit odds
- 1.1% chance of exploitation in the next 30 days (EPSS).
- Fix
- A patch, advisory or fixed version is referenced. Upgrade or apply it.
Timeline
- PublishedDisclosed publicly on CVE.org and NVD
- Last updatedMost recent change to the record
Why it ranks here
- Exploited in the wild: no, CISA does not list it.
- Exploit odds: 1.1% in the next 30 days (EPSS).
- Severity: 6.4 MEDIUM (CVSS).
- Fix: a patch or advisory is linked.
Details
- Published
- Last modified
- Exploit probability
- 1.1% · EPSS, next 30 days
- Weakness
- CWE-1329
- Record status
- Analyzed
Affected
- Microsoft Windows 10 1607 < 10.0.14393.8783
- Microsoft Windows 10 1809 < 10.0.17763.8276
- Microsoft Windows 10 21h2 < 10.0.19044.6809
- Microsoft Windows 10 22h2 < 10.0.19045.6809
- Microsoft Windows 11 23h2 < 10.0.22631.6491
- Microsoft Windows 11 24h2 < 10.0.26100.7623
- Microsoft Windows 11 25h2 < 10.0.26200.7623
- Microsoft Windows Server 2012
Attack profile CVSS 3.1 · 6.4
- Attack vector
- Local
- Complexity
- High
- Privileges needed
- High
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
Raw vector
CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H
Is it in your code?
Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.
Read https://cve-list.com/agent/cve/CVE-2026-21265.md and follow it. Check whether this project is affected by CVE-2026-21265. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.
