CVE-2025-52916 is a vulnerability identified in Yealink's RPS (Redirection and Provisioning Service) product versions prior to June 4, 2025. The vulnerability is classified under CWE-307, which pertains to improper restriction of excessive authentication attempts. Specifically, Yealink RPS lacks adequate limits on the number of serial number (SN) verification attempts, allowing an attacker to perform brute-force enumeration of the last five digits of device serial numbers. This flaw enables an adversary to systematically guess and verify serial numbers without being blocked or throttled by the system. The vulnerability has a CVSS 3.1 base score of 2.2, indicating a low severity level. The vector metrics show that exploitation requires network access (AV:N), high attack complexity (AC:H), privileges (PR:H), no user interaction (UI:N), and impacts only confidentiality (C:L) with no effect on integrity or availability. No known exploits are currently reported in the wild, and no patches have been linked yet. The vulnerability primarily affects the confidentiality of device information by potentially exposing valid serial numbers through enumeration, which could be leveraged in subsequent targeted attacks or device impersonation scenarios.

For European organizations using Yealink RPS for device provisioning and management, this vulnerability could lead to unauthorized disclosure of device serial numbers. While the direct impact on system integrity and availability is negligible, the exposure of serial numbers may facilitate further reconnaissance and targeted attacks, such as unauthorized device registration, spoofing, or social engineering campaigns. Given that Yealink devices are widely used in enterprise telephony and unified communications across Europe, attackers could leverage this information to undermine trust in communication infrastructure or gain footholds for more sophisticated attacks. However, the requirement for high privileges and network access limits the ease of exploitation, reducing immediate risk. Nonetheless, organizations with large deployments of Yealink devices should consider this vulnerability as part of their risk management, especially in sectors where secure communications are critical, such as government, finance, and healthcare.

To mitigate this vulnerability, European organizations should implement the following specific measures: 1) Monitor and restrict access to the Yealink RPS interface, ensuring that only authorized personnel with necessary privileges can perform SN verification. 2) Employ network segmentation and firewall rules to limit exposure of the RPS service to trusted internal networks or VPNs. 3) Implement custom rate limiting or anomaly detection on SN verification requests to detect and block brute-force attempts, even if the vendor patch is not yet available. 4) Maintain strict access control policies and audit logs to detect suspicious activities related to serial number enumeration. 5) Stay updated with Yealink security advisories and apply patches promptly once released. 6) Consider additional authentication mechanisms or multi-factor authentication for accessing provisioning services to increase the difficulty of unauthorized access. 7) Educate IT staff about this vulnerability and encourage vigilance against potential follow-on attacks that could leverage enumerated serial numbers.