CVE-2025-20726 is a heap overflow vulnerability (CWE-122) identified in the modem firmware of a wide range of MediaTek chipsets, including models MT2735 through MT8893 series. The root cause is an incorrect bounds check in the modem's code, which allows an out-of-bounds write to occur. This memory corruption can be triggered remotely when a user equipment (UE) connects to a maliciously controlled rogue base station. The attacker can exploit this flaw to escalate privileges on the device without requiring any additional execution privileges or user interaction, making the attack vector highly accessible. The affected modem firmware versions are LR12A, NR15, NR16, NR17, and NR17R. The vulnerability impacts confidentiality, integrity, and availability by potentially allowing attackers to execute arbitrary code or disrupt modem operations. The CVSS v3.1 score is 7.5, reflecting a high severity with network attack vector, high impact on all security properties, but requiring low privileges and high attack complexity. No public exploits have been reported yet, but the broad chipset coverage and remote exploitation capability make this a critical concern for mobile device security. The vulnerability was reserved in November 2024 and published in November 2025, with patches expected from MediaTek though no direct patch links are provided in the data.

For European organizations, this vulnerability poses a significant risk due to the widespread use of MediaTek chipsets in smartphones, IoT devices, and embedded systems. Attackers controlling rogue base stations could remotely compromise devices without user interaction, leading to unauthorized access to sensitive communications, data leakage, or device disruption. Critical sectors such as finance, government, healthcare, and telecommunications could be targeted to intercept or manipulate communications. The vulnerability could also undermine trust in mobile networks and complicate compliance with data protection regulations like GDPR if personal data is compromised. Additionally, the potential for privilege escalation on devices could facilitate further lateral movement or persistent access within organizational networks. The risk is amplified in environments where devices connect to untrusted or public cellular networks, common in enterprise mobility scenarios.

Organizations should prioritize deploying firmware updates from device manufacturers that incorporate MediaTek's patches for the affected modem versions. Since direct patch links are not provided, coordination with device vendors and carriers is essential to ensure timely updates. Network operators and enterprises should implement detection and blocking mechanisms for rogue base stations using radio frequency monitoring tools and anomaly detection systems. Employing mobile threat defense (MTD) solutions that can identify suspicious network behavior can further reduce risk. Restricting device connectivity to trusted networks and educating users about the dangers of connecting to unknown cellular networks can help mitigate exposure. For high-risk environments, consider using devices with alternative chipsets or additional security layers. Regular security assessments and penetration testing focusing on mobile device security posture will help identify residual risks.