CVE-2025-20634 is a vulnerability classified under CWE-787 (Out-of-bounds Write) found in the modem firmware of a wide range of MediaTek chipsets including MT2737, MT6813, MT6835 series, MT6878 series, MT6895 series, MT6980 series, MT6983 series, MT6985 series, MT6989 series, MT6990, MT6991, MT8673, MT8676, MT8678, MT8795T, MT8798, and MT8863. The issue stems from a missing bounds check in the modem's code, which allows an attacker controlling a rogue base station to send specially crafted signals that cause the modem to write data outside the intended memory boundaries. This out-of-bounds write can lead to remote code execution on the modem, compromising the device's confidentiality, integrity, and availability. The vulnerability affects modem firmware versions NR16, NR17, and NR17R. Exploitation does not require user interaction or any privileges, making it feasible to attack devices silently when they connect to a malicious base station. The vulnerability was published on February 3, 2025, with a CVSS v3.1 score of 8.8 (AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H), indicating a high-severity remote attack vector with no privileges or user interaction needed. Although no exploits are currently known in the wild, the potential for impactful attacks on mobile devices and IoT equipment using these chipsets is significant. The vendor has assigned a patch ID (MOLY01289384) and issue ID (MSV-2436), but no public patch links are currently available. This vulnerability is particularly critical because it targets the modem firmware, a core component responsible for cellular communications, and could be leveraged to compromise device security at a fundamental level.

For European organizations, the impact of CVE-2025-20634 is substantial. Devices using affected MediaTek chipsets are widespread in smartphones, IoT devices, and embedded systems, many of which are integral to enterprise operations and critical infrastructure. Successful exploitation could allow attackers to execute arbitrary code remotely on the modem, potentially leading to interception or manipulation of communications, device takeover, and disruption of services. This threatens confidentiality by exposing sensitive data transmitted over cellular networks, integrity by allowing malicious code execution, and availability by causing device or network outages. Telecommunications providers, mobile network operators, and industries relying on cellular connectivity (e.g., manufacturing, transportation, healthcare) are particularly vulnerable. The ability to exploit this vulnerability without user interaction or privileges increases the risk of large-scale attacks, especially in environments where rogue base stations could be deployed. European countries with advanced telecom infrastructure and high mobile device penetration face elevated risks, potentially impacting national security and economic stability.

To mitigate CVE-2025-20634, European organizations should prioritize the following actions: 1) Monitor MediaTek and device vendors for official patches corresponding to patch ID MOLY01289384 and apply them promptly to all affected devices and firmware versions (NR16, NR17, NR17R). 2) Implement network-level defenses to detect and block rogue base stations, including enhanced base station authentication and anomaly detection systems within mobile network infrastructure. 3) Employ mobile device management (MDM) solutions to inventory devices with affected chipsets and enforce timely updates. 4) Educate users and administrators about the risks of connecting to untrusted cellular networks, especially in sensitive environments. 5) Collaborate with telecom providers to enhance monitoring for suspicious base station activity and coordinate incident response. 6) For critical IoT deployments, consider network segmentation and fallback communication methods to reduce exposure. 7) Engage in threat intelligence sharing within industry groups to stay informed about emerging exploits or attack campaigns targeting this vulnerability. These measures go beyond generic patching by emphasizing detection, prevention of rogue infrastructure, and operational readiness.