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

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 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 01/23/2026).

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

• Operating System

Vendor

• Microsoft

Name

• Windows

Version

• 10 21H2
• 10 22H2
• 10 1607
• 10 1809
• 11 23H2
• 11 24H2
• 11 25H2
• Server 2012
• Server 2012 R2
• Server 2016
• Server 2019
• Server 2022
• Server 2022 23H2
• Server 2025

License

• commercial

Website

• Vendor: https://www.microsoft.com/
• Product: https://www.microsoft.com/en-us/windows

CPE 2.3info

• 🔒
• 🔒
• 🔒

CPE 2.2info

• 🔒
• 🔒
• 🔒

CVSSv4info

CVSSv3info

CVSSv2info

Exploitinginfo

Threat Intelligenceinfo

Countermeasuresinfo

Timelineinfo

Sourcesinfo

Entryinfo

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

Discussion