net-snmp before 5.8.1.pre1 has a double free in usm_free_usmStateReference in snmplib/snmpusm.c via an SNMPv3 GetBulk request. NOTE: this affects net-snmp packages shipped to end users by multiple Linux distributions, but might not affect an upstream release.
https://www.oracle.com/security-alerts/cpujan2021.html
https://usn.ubuntu.com/4410-1/
https://security.gentoo.org/glsa/202008-12
https://github.com/net-snmp/net-snmp/commit/5f881d3bf24599b90d67a45cae7a3eb099cd71c9