SCRAM-SHA-256 authentication accepted without verifying the server's final
signature. The vendor advisory and GHSA list the affected range as
>= 5.6-alpha1, < 5.6.1. ScramScheme, ScramSchemeFactory and ScramExtension
were added by commit 5e73e17ae ("Add SCRAM-SHA-256 (RFC 7804) (#718)"),
first released in 5.6-alpha1. At rel/v5.5.1 no httpclient5 main source
mentions SCRAM (git grep -i scram finds nothing), so the vulnerable code
does not exist. Trivy still flags 5.5.1.