USN-8431-1: Ruby vulnerabilities

CVE-2026-42256 net-imap: Denial of service via high iteration count for `SCRAM-*` authentication

CVE-2026-42246 net-imap vulnerable to STARTTLS stripping via invalid response timing

CVE-2026-42257 net-imap: Command Injection via "raw" arguments to multiple commands

CVE-2026-42258 net-imap: Command Injection via unvalidated Symbol inputs