An HTTPS record has no-default-alpn but no alpn parameter.

SVCB_ALPN_MISSING · Severity: Error

• ErrorSVCB_ALPN_MISSING

  An HTTPS record has no-default-alpn but no alpn parameter.

  no-default-alpn removes the default protocol, so the record must also say which protocols it offers in alpn (RFC 9460 section 7.1). Without it the record offers nothing, and clients ignore it.

  Recommendation: Add alpn, for example alpn=h2, or drop no-default-alpn.

Reported by

• HTTPS record check

Available through the API

• HTTPS record check API

Related findings

• Warning SVCB_ALIAS_CONFLICT An HTTPS AliasMode record sits beside other HTTPS records.
• Warning SVCB_ALIAS_WITH_PARAMS An HTTPS AliasMode record has parameters, which clients ignore.
• Info SVCB_ECH The HTTPS record publishes an Encrypted Client Hello configuration.
• Error SVCB_INVALID An HTTPS record cannot be read.
• Error SVCB_MANDATORY_MISSING An HTTPS record lists a mandatory parameter that it does not have.
• Info SVCB_NOT_FOUND The name publishes no HTTPS record.

All findings