CVE-2025-20726 is a heap overflow vulnerability classified under CWE-122, found in the modem firmware of numerous MediaTek chipsets, including but not limited to MT2735, MT6739, MT6761, MT6762 series, MT6771, MT6885, MT6895, MT6980 series, and many others. The root cause is an improper bounds check in the modem's code, which allows an out-of-bounds write to heap memory. This flaw can be triggered remotely when a user equipment (UE) device connects to a maliciously controlled rogue base station. Because the modem firmware operates at a low level with privileged access, the attacker can escalate privileges remotely without requiring any user interaction or additional execution privileges. The affected modem firmware versions include LR12A, NR15, NR16, NR17, and NR17R. The vulnerability could allow attackers to execute arbitrary code or cause denial of service within the modem, potentially compromising the confidentiality, integrity, and availability of the device's communication functions. Although no public exploits are known, the broad range of affected chipsets and the nature of the vulnerability make it a significant risk. MediaTek has acknowledged the issue (Issue ID: MSV-4622) and assigned Patch ID MOLY01672598, but no public patch links are currently available. The vulnerability's exploitation vector requires proximity or control over cellular infrastructure, specifically a rogue base station, which is a realistic threat in targeted attacks or hostile environments.

For European organizations, this vulnerability poses a substantial risk particularly to enterprises and individuals relying on mobile devices powered by MediaTek chipsets for critical communications. The ability to escalate privileges remotely without user interaction means attackers could compromise device modems to intercept, manipulate, or disrupt cellular communications. This could lead to data breaches, espionage, or denial of service affecting mobile connectivity. Industries such as telecommunications, finance, government, and critical infrastructure that depend on secure mobile communications are at heightened risk. The vulnerability also threatens the integrity of mobile networks and could be exploited in targeted attacks using rogue base stations, which have been documented in Europe. The widespread use of MediaTek chipsets in smartphones, IoT devices, and embedded systems across Europe amplifies the potential impact. Additionally, compromised devices could serve as entry points for lateral movement within corporate networks, increasing the overall threat landscape.

European organizations and device users should prioritize the following mitigations: 1) Monitor for firmware updates from device manufacturers and MediaTek addressing CVE-2025-20726 and apply patches promptly. 2) Employ network detection systems capable of identifying rogue base stations or anomalous cellular network behavior to prevent devices from connecting to malicious infrastructure. 3) Enforce strict mobile device management (MDM) policies to control device firmware versions and restrict connections to untrusted networks. 4) Educate users about the risks of connecting to unknown or suspicious cellular networks, especially in sensitive environments. 5) Collaborate with mobile network operators to enhance detection and mitigation of rogue base stations within their infrastructure. 6) For critical deployments, consider using devices with alternative chipsets or additional security layers until patches are available. 7) Implement anomaly detection on network traffic to identify potential exploitation attempts targeting modem vulnerabilities. These steps go beyond generic advice by focusing on infrastructure-level detection and organizational policy enforcement tailored to this modem-specific threat.