CVE-2025-28172 is a vulnerability affecting Grandstream Networks UCM6510 devices running firmware version 1.0.20.52 and earlier. The vulnerability arises from improper restriction of excessive authentication attempts, allowing an attacker to perform an unlimited number of login attempts without triggering account lockout or other protective mechanisms. This flaw enables brute force attacks where an attacker systematically tries different passwords against a targeted account until successful authentication is achieved. The lack of rate limiting or account lockout mechanisms significantly lowers the barrier for attackers to compromise accounts, potentially granting unauthorized access to the device's administrative interface or user accounts. Given that UCM6510 is a Unified Communications Manager device used for VoIP telephony and related services, unauthorized access could lead to interception or manipulation of voice communications, disruption of telephony services, and exposure of sensitive organizational communications data. Although no known exploits are currently reported in the wild, the vulnerability's nature makes it a critical risk if exploited. No CVSS score has been assigned yet, but the vulnerability's characteristics warrant serious attention.

For European organizations, exploitation of this vulnerability could have severe consequences. The UCM6510 is commonly deployed in enterprise environments to manage voice communications infrastructure. Unauthorized access through brute force could allow attackers to eavesdrop on calls, manipulate call routing, or disrupt telephony services, impacting business continuity and confidentiality. This could lead to financial losses, reputational damage, and regulatory compliance issues, especially under GDPR where communication data privacy is strictly regulated. Additionally, compromised devices could be leveraged as pivot points for lateral movement within corporate networks, increasing the risk of broader cyberattacks. Organizations in sectors with high reliance on secure communications, such as finance, healthcare, and government, are particularly at risk. The absence of known exploits currently provides a window for proactive mitigation before widespread exploitation occurs.

To mitigate this vulnerability, European organizations should immediately assess their deployment of Grandstream UCM6510 devices and verify firmware versions. Upgrading to a patched firmware version, once released by Grandstream, is the most effective mitigation. Until a patch is available, organizations should implement compensating controls such as: 1) Restricting administrative interface access to trusted IP addresses or VPNs to limit exposure to potential attackers. 2) Enabling network-level rate limiting or intrusion prevention systems to detect and block brute force attempts targeting the device. 3) Enforcing strong, complex passwords and regular password rotation policies for all accounts on the device. 4) Monitoring authentication logs for unusual login attempts and setting up alerts for potential brute force activity. 5) Segmenting voice network infrastructure from general IT networks to contain potential compromises. 6) Considering multi-factor authentication if supported by the device or through external access controls. These measures will reduce the likelihood of successful exploitation and limit potential damage.