A vulnerability in the User Data Services (UDS) API of Cisco Unified Communications Manager (Unified CM) could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on the management GUI. The vulnerability is due to improper validation of input parameters in the UDS API requests. An attacker could exploit this vulnerability by sending a crafted request to the UDS API of an affected device. A successful exploit could allow the attacker to make the A Cisco DB service quit unexpectedly, preventing admin access to the Unified CM management GUI. Manual intervention may be required to restore normal operation. Software versions 10.5, 11.5, 12.0, 12.5 are affected.