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Clarify requirements for root certificates and their scopes.
Updated validity period for newly minted Root CAs to a maximum of 10 years, effective July 1, 2026.
Added clarification on Microsoft’s classification of suspect code and its relation to the Unified Security Operations criteria.
Added requirement for Certificate Authorities to disclose incident reports in Bugzilla and notify Microsoft.
March Update
dzacharo
reviewed
Mar 12, 2026
| - This EKU is used for signing documents within Office. It isn't required for other document signing uses. | ||
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| **3.4.3** Effective for all root certificates submitted on or after July 1, 2026: | ||
| Effective for all root certificates submitted on or after July 1, 2026, root certificates MUST be limited in scope and dedicated to a clearly defined trust purpose. |
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Considering that the id-kp-clientAuth KeyPurposeId is allowed further below, please consider making the following change:
Suggested change
| Effective for all root certificates submitted on or after July 1, 2026, root certificates MUST be limited in scope and dedicated to a clearly defined trust purpose. | |
| Effective for all root certificates submitted on or after July 1, 2026, root certificates MUST be limited in scope and dedicated to clearly defined trust purposes. |
| **3.1.7.** Root Key Sizes must meet the requirements detailed in "Signature Requirements" below. | ||
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| **3.1.8.** Newly minted Root CAs must be valid for a minimum of eight years, and a maximum of 25 years, from the date of submission. | ||
| **3.1.8.** Newly minted Root CAs must be valid for a maximum 10 years, from the date of submission, effective July 1, 2026. |
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It seems this requirement limits the usage of cross-signing chains, leading to breakage on devices older than 10 years old. I'm just wondering if this is also an intended outcome?
| Effective for all root certificates submitted on or after July 1, 2026, root certificates MUST be limited in scope and dedicated to a clearly defined trust purpose. | ||
| Root certificates authorized for Server Authentication, S/MIME, or Code Signing MUST each be separate and independent trust anchors. A root certificate MUST NOT be authorized for more than one of these EKUs. | ||
| A root certificate authorized for Code Signing MAY also be authorized for Client Authentication and Time Stamping. A root certificate authorized for Server Authentication OR SMIME MAY also be authorized for Client Authentication. | ||
| No EKU combinations other than those explicitly permitted above are allowed.Root certificates submitted prior to January 1, 2027 that assert multiple EKUs will continue to be trusted unless otherwise directed by Microsoft. |
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The list above does not allow for the issuance of Code Signing Certificates
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