A vulnerability in the restricted security domain implementation of Cisco Application Policy Infrastructure Controller (APIC) could allow an authenticated, remote attacker to modify the behavior of default system policies, such as quality of service (QoS) policies, on an affected system.&nbsp;This vulnerability is due to improper access control when restricted security domains are used to implement multi-tenancy. An attacker with a valid user account associated with a restricted security domain could exploit this vulnerability. A successful exploit could allow the attacker to read, modify, or delete child policies created under default system policies, which are implicitly used by all tenants in the fabric, resulting in disruption of network traffic. Exploitation is not possible for policies under tenants that an attacker has no authorization to access.