Cisco recently patched the high-severity flaw, which could allow remote, unauthenticated attackers to launch DoS attacks against its popular small business switches. The vulnerability stems from the IPv6 packet processing engine in the switches. It s not the first time that end of life (EoL) has stopped Cisco from issuing patches for these specific switches when they were vulnerable. The flaw (CVE-2020-3363) is due to insufficient validation of incoming IPv6 traffic.
Source: https://threatpost.com/high-severity-cisco-dos-flaw-small-business-switches/158124/