Django fails to prevent reuse of a partially-initialized connection after a failed `STARTTLS` handshake

An issue was discovered in Django 6.0 before 6.0.6 and 5.2 before 5.2.15. django.core.mail.backends.smtp.EmailBackend in Django fails to prevent reuse of a partially-initialized connection after a failed STARTTLS handshake when failsilently=True, which allows on-path network attackers to read ema...