CVE-2026-20404 is a critical vulnerability classified under CWE-787 (Out-of-bounds Write) affecting numerous MediaTek modem chipsets, including models MT2735 through MT8893. The vulnerability stems from improper input validation within the modem firmware, which can be triggered remotely when a user equipment (UE) connects to a maliciously controlled rogue base station. This rogue base station can send crafted inputs that cause the modem to perform out-of-bounds memory writes, leading to a system crash and resulting in a denial of service condition. The attack vector does not require any user interaction or elevated privileges, making it feasible for attackers to disrupt service silently and remotely. The affected modem versions include NR15, NR16, NR17, and NR17R, which are commonly embedded in mobile devices and IoT equipment. Although no public exploits have been reported yet, the vulnerability's nature and broad chipset coverage pose a significant risk. The patch has been identified (MOLY01689248), but no direct patch links are provided. This vulnerability primarily threatens the availability of affected devices, potentially causing network outages or degraded service quality. The broad range of affected chipsets indicates a widespread impact across various device manufacturers using MediaTek modems.

For European organizations, the primary impact of CVE-2026-20404 is the potential for remote denial of service attacks against devices using vulnerable MediaTek modems. Telecommunications providers, IoT device manufacturers, and enterprises relying on mobile connectivity could experience service disruptions, affecting business continuity and operational reliability. Critical infrastructure relying on cellular connectivity, such as smart grids, transportation systems, and emergency services, may face increased risk of outages or degraded performance. The lack of required user interaction and the ability to exploit via rogue base stations make this vulnerability particularly dangerous in dense urban environments where attackers could deploy such stations covertly. Additionally, the disruption could lead to reputational damage and regulatory scrutiny under European data protection and network security laws. The widespread use of MediaTek chipsets in consumer and industrial devices across Europe amplifies the potential scope of impact.

To mitigate CVE-2026-20404, European organizations should prioritize the following actions: 1) Coordinate with device manufacturers and vendors to obtain and deploy the official firmware patches (MOLY01689248) for all affected MediaTek modem chipsets as soon as they become available. 2) Implement network-level defenses to detect and block rogue base stations, including the use of radio frequency monitoring tools and anomaly detection systems within cellular networks. 3) Employ device-level security controls such as modem firmware integrity verification and secure boot mechanisms to prevent unauthorized firmware modifications. 4) For critical infrastructure, consider deploying redundant communication paths and failover mechanisms to maintain service availability during potential attacks. 5) Educate network operations teams about the threat of rogue base stations and establish incident response procedures to quickly isolate and remediate affected devices. 6) Collaborate with mobile network operators to enhance base station authentication and validation protocols to reduce the risk of rogue station exploitation. These targeted measures go beyond generic patching by addressing the attack vector and operational resilience.