# 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.

- **Severity:** Medium 6.4 (`CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C`)
- **Exploited in the wild:** Not known
- **Login needed:** An administrator
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 13 Jan 2026
- **Updated:** 30 Jul 2026
- **Also known as:** GHSA-xqxc-72vf-v8f5, UBUNTU-CVE-2026-21265

## 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 (Reliance on Component That is Not Updateable)

## Which versions are affected by CVE-2026-21265?

It affects 13 products.


Products: Microsoft Windows 10 1607, Microsoft Windows 10 1809, Microsoft Windows 10 21h2, Microsoft Windows 10 22h2, Microsoft Windows 11 23h2, Microsoft Windows 11 24h2, Microsoft Windows 11 25h2, Microsoft Windows Server 2012, Microsoft Windows Server 2016, Microsoft Windows Server 2019, Microsoft Windows Server 2022, Microsoft Windows Server 2022 23h2, Microsoft Windows Server 2025.

## 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](https://insights.sbomify.com/CVE-2026-33824/): Microsoft Internet Key Exchange (IKE) Service Extensions Double Free (critical 9.8, exploited in the wild)
- [CVE-2026-21510](https://insights.sbomify.com/CVE-2026-21510/): Microsoft Windows Shell Protection Mechanism Failure (high 8.8, exploited in the wild)
- [CVE-2026-21513](https://insights.sbomify.com/CVE-2026-21513/): Microsoft MSHTML Framework Protection Mechanism Failure (high 8.8, exploited in the wild)
- [CVE-2023-32049](https://insights.sbomify.com/CVE-2023-32049/): Microsoft Windows Defender SmartScreen Security Feature Bypass (high 8.8, exploited in the wild)
- [CVE-2023-29360](https://insights.sbomify.com/CVE-2023-29360/): Microsoft Streaming Service Untrusted Pointer Dereference (high 8.4, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-21265 and fix it if it is affected.

What it is: 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.
Exploitation: There is no known exploitation of CVE-2026-21265 in the wild and no public exploit code.

Affected product: Microsoft Windows 10 1607. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-21265/ (Markdown: https://insights.sbomify.com/CVE-2026-21265/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-21265
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-21265
- OSV: https://osv.dev/vulnerability/CVE-2026-21265

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-21265/
Summaries are generated and may contain mistakes; the official description above is the record.