CVE-2025-20757 is a vulnerability classified under CWE-617 (Reachable Assertion) found in the modem firmware of numerous MediaTek chipsets including MT2735, MT6833 series, MT6853 series, MT6873 series, MT6880 series, MT6890 series, and others. The flaw arises from improper input validation within the modem's handling of signals when a user equipment (UE) connects to a base station. An attacker controlling a rogue base station can send crafted inputs that trigger an assertion failure, causing the modem system to crash, resulting in a denial of service (DoS). The vulnerability does not require user interaction and does not grant the attacker additional execution privileges beyond causing the crash. The attack vector is network-based, with a high attack complexity, and requires low privileges (the attacker must control a rogue base station). The modem version affected is NR15. The impact is limited to availability, with no confidentiality or integrity compromise reported. Although no known exploits have been observed in the wild, the vulnerability poses a risk to mobile devices using these chipsets, potentially disrupting cellular connectivity and services. MediaTek has assigned a patch ID (MOLY01673751) and issue ID (MSV-4644), indicating a fix is available or forthcoming. The vulnerability was reserved in November 2024 and published in December 2025, reflecting a recent discovery and disclosure timeline.

For European organizations, this vulnerability could disrupt mobile communications by causing device modems to crash when connecting to rogue base stations. This can impact availability of cellular services, which is critical for enterprises relying on mobile connectivity for operations, remote work, IoT deployments, and emergency communications. Telecommunications providers and infrastructure operators may face increased risk of service degradation or outages if attackers deploy rogue base stations targeting vulnerable devices. Critical sectors such as finance, healthcare, transportation, and government services that depend on uninterrupted mobile connectivity could experience operational interruptions. The risk is heightened in environments where mobile devices with affected MediaTek chipsets are prevalent. Although the vulnerability does not compromise data confidentiality or integrity, the denial of service can lead to loss of communication, impacting business continuity and safety-critical applications. The lack of user interaction requirement and remote exploitation capability increase the threat surface. However, the high attack complexity and need for a rogue base station limit the ease of exploitation to well-resourced attackers.

European organizations should prioritize deploying the vendor-provided patches (MOLY01673751) as soon as they become available to remediate the vulnerability in affected modem firmware. Network operators and enterprises should implement detection and mitigation strategies against rogue base stations, such as using radio frequency monitoring tools and anomaly detection systems to identify unauthorized base stations. Mobile device management (MDM) solutions can be used to enforce firmware updates and monitor device health. Organizations should educate users and IT staff about the risks of connecting to untrusted cellular networks and encourage the use of trusted network providers. For critical infrastructure, deploying multi-factor communication channels and fallback connectivity options can reduce reliance on vulnerable modems. Collaboration with telecom providers to share threat intelligence and coordinate responses to rogue base station threats is recommended. Regular security assessments and penetration testing focusing on cellular network security can help identify exposure. Finally, maintaining up-to-date inventories of devices with affected chipsets will aid in targeted remediation efforts.