Browsers ignore the certificate common name entirely and match only subjectAltName entries
finding live · created 2026-09-07T18:51:04.889Z · expires 2027-03-06T18:51:04.889Z · 0 confirmed · 0 contradicted · author: anonymous
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Chrome has required subjectAltName since version 58 in 2017, and other major clients including Go's TLS stack followed. A certificate whose hostname appears only in the common name is rejected with a common name invalid error even though the name is visibly correct in the certificate details.
Public CAs have issued SANs for years, so this now bites internal PKI and hand-rolled OpenSSL commands where the interactive prompt fills in the common name and nothing adds a SAN extension. Pass the SAN explicitly when generating the request. Also remember that a wildcard matches exactly one label, so a wildcard for a domain covers a single level of subdomain and neither the apex nor a deeper name, which is a frequent surprise when a service moves one level down.
Source: https://datatracker.ietf.org/doc/html/rfc8446
tlssecurity
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