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2,507 bytes added, 22:06, 12 November 2018
Add Nov Communications
The following are communications that have been sent to Certification Authorities participating in [[CA | Mozilla's root program.]] If you have questions regarding these communications, please first review related discussions in the forum. If your questions cannot be answered in that forum, then please send email to
== November 2018 CA Communication (Underscores in dNSNames) ==
On November 12, 2018, the following message was sent to all CAs in the Mozilla program, alerting them to CA/Browser Forum SC12 that established a brief sunset period for the use of underscore characters in dNSNames in publicly-trusted TLS certificates.
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Dear Certification Authority,
The CA/Browser Forum recently approved [1] a clarification to the “Baseline Requirements for the Issuance and Management of Publicly-Trusted Certificates” (BRs) that may affect you. Domain names containing underscore (“_”) characters are not permitted to be encoded as dNSName types in the subjectAlternativeName (SAN) field of BR-compliant certificates. This requirement derives from section of RFC 5280 that the BRs require CAs to comply with by reference.
Section of the BRs will add the following language that clarifies the existing requirement and adds a short time in which CAs must discontinue the use of underscore characters in dNSNames:
Prior to April 1, 2019, certificates containing underscore characters (“_”) in domain labels in dNSName entries MAY be issued as follows:
* dNSName entries MAY include underscore characters such that replacing all underscore characters with hyphen characters (“-“) would result in a valid domain label, and;
* Underscore characters MUST NOT be placed in the left most domain label, and;
* Such certificates MUST NOT be valid for longer than 30 days.
All certificates containing an underscore character in any dNSName entry and having a validity period of more than 30 days MUST be revoked prior to January 15, 2019.
After April 30, 2019, underscore characters (“_”) MUST NOT be present in dNSName entries.
This new language will go into effect on December 10, 2019 when the IPR review period for ballot SC12 [1] is completed. At that time, CAs must be prepared to stop issuing publicly-trusted TLS certificates containing the underscore character in any dNSName with validity periods of more than 30 days.
As a participant in Mozilla's CA Certificate Program, we want you to be aware of this important change, and ask that you take any necessary steps to comply. No further action related to this change is requested at this time.
Wayne Thayer
Mozilla CA Program Manager
=== November 2018 Responses ===
* No survey was included in this CA Communication
== September 2018 CA Communication ==

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