CVE-2023-25117 is a stack-based buffer overflow vulnerability identified in the vtysh_ubus binary of the Milesight UR32L device firmware version 32.3.0.5. The vulnerability stems from unsafe usage of the sprintf function within the set_openvpn_client function, specifically when handling the local_virtual_ip and local_virtual_mask parameters. This unsafe coding practice allows an attacker with high privileges to craft malicious HTTP requests that overflow the stack buffer, potentially leading to arbitrary code execution on the device. The vulnerability requires that the attacker already has high privileges, implying some level of prior access or compromise. The flaw affects confidentiality, integrity, and availability since arbitrary code execution can lead to data leakage, device manipulation, or denial of service. The CVSS v3.1 score is 7.2 (high), reflecting network attack vector, low attack complexity, required privileges, no user interaction, and full impact on confidentiality, integrity, and availability. Currently, there are no publicly known exploits in the wild, and no official patches have been linked yet. The vulnerability is classified under CWE-121 (stack-based buffer overflow), a common and dangerous software weakness. The affected product, Milesight UR32L, is a network device often used in industrial and enterprise environments for routing and VPN services. The vulnerability specifically impacts the OpenVPN client configuration functionality, which is critical for secure remote access. Exploitation could allow attackers to execute arbitrary code remotely, potentially compromising the device and the network it protects.

For European organizations, this vulnerability poses a significant risk, especially for those relying on Milesight UR32L devices in their network infrastructure. Successful exploitation can lead to full compromise of the device, enabling attackers to intercept or manipulate sensitive communications, disrupt network availability, or pivot to other internal systems. Critical sectors such as energy, manufacturing, and telecommunications that use these devices for secure VPN connections are particularly vulnerable. The impact extends to confidentiality breaches, integrity violations through unauthorized configuration changes, and availability disruptions via device crashes or persistent compromise. Given the network-exposed attack vector and high privileges required, insider threats or attackers who have already breached perimeter defenses pose the greatest risk. The absence of known exploits in the wild reduces immediate risk but does not eliminate the urgency for mitigation, as public disclosure may prompt attackers to develop exploits. European organizations must consider the potential for targeted attacks against critical infrastructure and sensitive networks using these devices.

1. Immediately restrict HTTP access to the vtysh_ubus interface by implementing strict firewall rules limiting access to trusted management IPs only. 2. Monitor network traffic for unusual or malformed HTTP requests targeting the OpenVPN client configuration endpoints to detect potential exploitation attempts. 3. Employ network segmentation to isolate Milesight UR32L devices from less trusted network zones and reduce attack surface. 4. Regularly audit device configurations and logs for signs of compromise or unauthorized changes. 5. Engage with the vendor to obtain and apply official patches or firmware updates addressing this vulnerability as soon as they become available. 6. If patching is delayed, consider disabling or restricting OpenVPN client configuration features temporarily if operationally feasible. 7. Implement multi-factor authentication and strong access controls to reduce the risk of high-privilege account compromise. 8. Conduct internal vulnerability assessments and penetration tests focusing on network devices to identify and remediate similar issues proactively.