CVE-2025-20790 is a vulnerability identified in multiple MediaTek modem chipsets (including MT2735, MT6833 series, MT6853 series, MT6873 series, MT6880 series, MT6890 series, MT8675, MT8771, MT8791 series, and MT8797) caused by a NULL pointer dereference (CWE-476) due to improper input validation in the modem firmware (Modem NR15). This flaw allows an attacker controlling a rogue base station to trigger a system crash remotely by sending malformed input to the modem when a user equipment (UE) connects. The attack vector requires no user interaction and no elevated privileges, making it a straightforward denial of service (DoS) attack against the modem’s availability. The vulnerability affects the modem’s ability to maintain network connectivity, potentially disrupting mobile communications. The CVSS v3.1 base score is 5.3 (medium severity) with vector AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H, indicating network attack complexity is high, low privileges are required, and no impact on confidentiality or integrity but high impact on availability. No public exploits are known at this time, and MediaTek has assigned a patch ID (MOLY01677581) and issue ID (MSV-4701) for remediation. The vulnerability is significant for mobile devices relying on these chipsets, particularly in environments where stable connectivity is critical.

For European organizations, this vulnerability poses a risk primarily to the availability of mobile communications. Telecommunications providers, enterprises relying on mobile broadband for critical operations, and public safety organizations could experience service disruptions if devices with affected MediaTek chipsets connect to rogue base stations. The DoS condition could interrupt voice, data, and emergency services, impacting operational continuity. While confidentiality and integrity are not directly affected, the loss of availability can degrade user experience and potentially hinder critical communications. The risk is heightened in sectors with stringent uptime requirements such as healthcare, transportation, and government. Additionally, the presence of rogue base stations is a known tactic in advanced persistent threat (APT) scenarios, increasing the threat landscape for sensitive European targets. The medium severity score reflects the limited scope of impact but acknowledges the potential for widespread disruption given the prevalence of MediaTek chipsets in mobile devices.

European organizations should implement a multi-layered mitigation strategy: 1) Ensure all affected devices receive the official firmware update or patch from device manufacturers incorporating MediaTek’s fix (MOLY01677581). 2) Network operators should monitor for and mitigate rogue base stations using radio frequency (RF) detection tools and anomaly detection systems to identify unauthorized base stations. 3) Deploy mobile device management (MDM) solutions to enforce timely updates and restrict connections to untrusted networks. 4) Educate users about the risks of connecting to unknown or suspicious cellular networks, especially in high-risk environments. 5) Collaborate with telecom providers to enhance network authentication and integrity checks to prevent rogue base station exploitation. 6) For critical infrastructure, consider fallback communication channels and redundancy to maintain availability during potential DoS events. 7) Regularly audit and test mobile network security posture to detect and respond to emerging threats related to rogue base stations.