In open62541 1.5.5, a server-side use-after-free exists in the local MonitoredItem callback path. The issue occurs when UA_Subscription_localPublish continues to use the current UA_Notification after a callback invokes UA_Server_deleteMonitoredItem for the current local MonitoredItem. This allows a remote attacker to cause a denial of service.
https://github.com/open62541/open62541/issues/8131
https://github.com/open62541/open62541/blob/v1.5.5/src/server/ua_subscription.c
https://github.com/open62541/open62541/blob/v1.5.5/src/server/ua_services_monitoreditem.c
https://github.com/open62541/open62541/blob/v1.5.5/include/open62541/server.h