I am experiencing this on a regular basis over the past week. It started in early 2020 with an occasional hang of the firewall. I have now been able to track access from external, unauthorized IP addresses originating ex-US, seemingly attacking our ASAv10 (running v9.6) and taking our service offline like a DoS. It appears that after the successful TLS1.2 negotiation the caller introduces something that causes the ASAv to go into a CPU intensive loop. All Syslog logging stops. The only solution has been reboot, which is unsatisfactory.
Log file attached. Any suggestions welcome.