CVE-2023-25124 identifies a stack-based buffer overflow vulnerability in the vtysh_ubus binary of the Milesight UR32L device firmware version v32.3.0.5. The root cause is the unsafe use of the sprintf function in the set_openvpn_client function, which processes the remote_subnet and remote_mask parameters from HTTP requests. This unsafe pattern allows an attacker with high privileges—meaning they already have some level of authenticated access—to craft malicious HTTP requests that overflow the stack buffer, leading to arbitrary code execution. The vulnerability affects confidentiality, integrity, and availability since an attacker could execute arbitrary code, potentially taking full control of the device, intercepting or manipulating VPN traffic, or causing denial of service. The CVSS v3.1 score is 7.2, reflecting network attack vector, low attack complexity, required privileges, no user interaction, and high impact on confidentiality, integrity, and availability. Although no public exploits are known yet, the vulnerability is critical due to the potential for remote code execution on network infrastructure devices. The affected product, Milesight UR32L, is a router often used in industrial and enterprise environments to provide VPN connectivity. The vulnerability specifically targets the OpenVPN client configuration interface, which is critical for secure remote access. The lack of a patch link indicates that a fix may not yet be publicly available, increasing the urgency for mitigation through access control and monitoring.

For European organizations, the impact of this vulnerability is significant. The Milesight UR32L is commonly deployed in industrial control systems, enterprise branch offices, and critical infrastructure sectors that rely on secure VPN connections for remote access. Exploitation could allow attackers to execute arbitrary code on these devices, leading to full compromise of the router. This could result in interception or manipulation of VPN traffic, unauthorized network access, disruption of business operations, and potential lateral movement within the network. Confidentiality of sensitive data transmitted over VPNs could be breached, integrity of network configurations compromised, and availability of network services disrupted. Given the high privileges required, exploitation is more likely in environments where administrative access is not tightly controlled. The absence of known exploits reduces immediate risk but does not eliminate the threat, especially from targeted attackers. European organizations in sectors such as manufacturing, energy, transportation, and government are particularly at risk due to their reliance on secure network infrastructure and VPN technologies.

1. Immediately restrict HTTP access to the vtysh_ubus interface to trusted administrators only, ideally via network segmentation and firewall rules. 2. Implement strict access controls and multi-factor authentication for administrative interfaces to reduce the risk of privilege escalation. 3. Monitor network traffic for unusual or malformed HTTP requests targeting the OpenVPN client configuration endpoints. 4. Regularly audit device configurations and logs for signs of exploitation attempts or anomalous behavior. 5. Engage with the vendor, Milesight, to obtain patches or firmware updates addressing this vulnerability as soon as they become available. 6. If patching is not immediately possible, consider disabling or restricting the vulnerable OpenVPN client configuration functionality temporarily. 7. Employ intrusion detection/prevention systems (IDS/IPS) with signatures or heuristics capable of detecting exploitation attempts targeting this vulnerability. 8. Educate network administrators about the risks and signs of exploitation related to this vulnerability to improve incident response readiness.