Microsoft Windows up to Server 2025 Secure Boot Certificate reliance on component that is not updateable

CVSS Meta Temp Score
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CTI Interest Score
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5.9$5k-$25k0.00

Summaryinfo

A vulnerability was found in Microsoft Windows. It has been rated as critical. Impacted is an unknown function of the component Secure Boot Certificate. Performing a manipulation results in reliance on component that is not updateable. This vulnerability is identified as CVE-2026-21265. The attack is only possible with local access. There is not any exploit available. To fix this issue, it is recommended to deploy a patch.

Detailsinfo

A vulnerability, which was classified as critical, was found in Microsoft Windows. This affects an unknown function of the component Secure Boot Certificate. The manipulation with an unknown input leads to a reliance on component that is not updateable vulnerability. CWE is classifying the issue as CWE-1329. The product contains a component that cannot be updated or patched in order to remove vulnerabilities or significant bugs. This is going to have an impact on confidentiality, integrity, and availability. The summary by CVE 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.

The weakness was released 01/13/2026 as confirmed security update guide (Website). It is possible to read the advisory at msrc.microsoft.com. This vulnerability is uniquely identified as CVE-2026-21265. The exploitability is told to be difficult. Attacking locally is a requirement. The exploitation needs additional levels of successful authentication. The technical details are unknown and an exploit is not publicly available. The pricing for an exploit might be around USD $5k-$25k at the moment (estimation calculated on 08/02/2026).

The vulnerability scanner Nessus provides a plugin with the ID 294825 (Linux Distros Unpatched Vulnerability : CVE-2026-21265), which helps to determine the existence of the flaw in a target environment.

Applying a patch is able to eliminate this problem. A possible mitigation has been published immediately after the disclosure of the vulnerability.

The vulnerability is also documented in the vulnerability database at Tenable (294825). Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

Productinfo

Type

Vendor

Name

Version

License

Website

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 6.4
VulDB Meta Temp Score: 5.9

VulDB Base Score: 6.4
VulDB Temp Score: 5.6
VulDB Vector: 🔒
VulDB Reliability: 🔍

Vendor Base Score (Microsoft): 6.4
Vendor Vector (Microsoft): 🔒

CNA Base Score: 6.4
CNA Vector (Microsoft): 🔒

CVSSv2info

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VectorComplexityAuthenticationConfidentialityIntegrityAvailability
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Reliance on component that is not updateable
CWE: CWE-1329
CAPEC: 🔒
ATT&CK: 🔒

Physical: Partially
Local: Yes
Remote: No

Availability: 🔒
Status: Unproven

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

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Nessus ID: 294825
Nessus Name: Linux Distros Unpatched Vulnerability : CVE-2026-21265

Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Patch
Status: 🔍

Reaction Time: 🔒
0-Day Time: 🔒
Exposure Time: 🔒

Timelineinfo

01/13/2026 VulDB entry created
01/13/2026 +0 days Advisory disclosed
01/13/2026 +0 days Countermeasure disclosed
08/02/2026 +201 days VulDB entry last update

Sourcesinfo

Vendor: microsoft.com
Product: microsoft.com

Advisory: msrc.microsoft.com
Status: Confirmed

CVE: CVE-2026-21265 (🔒)
GCVE (CVE): GCVE-0-2026-21265
GCVE (VulDB): GCVE-100-340851
scip Labs: https://www.scip.ch/en/?labs.20161215

Entryinfo

Created: 01/13/2026 20:01
Updated: 08/02/2026 16:28
Changes: 01/13/2026 20:01 (4), 01/13/2026 20:02 (32), 01/13/2026 20:05 (33), 01/23/2026 08:40 (2), 08/02/2026 16:28 (12)
Complete: 🔍
Cache ID: 216::103

Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

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