CVE-2025-20659 is an out-of-bounds read vulnerability classified under CWE-125 that affects numerous MediaTek modem chipsets, including models MT2735 through MT8863. The root cause is improper input validation within the modem firmware, which can be exploited remotely without requiring user interaction or elevated privileges. An attacker controlling a rogue base station can induce the vulnerable UE to process malformed input, leading to a system crash and denial of service. The affected modem firmware versions include LR12A, LR13, NR15, NR16, NR17, and NR17R. The vulnerability's CVSS 3.1 score is 6.5, indicating a medium severity level, with an attack vector of adjacent network (AV:A), low attack complexity (AC:L), no privileges required (PR:N), and no user interaction (UI:N). The impact is limited to availability, as confidentiality and integrity are not affected. No public exploits are known yet, but the extensive range of affected chipsets and the lack of required user interaction increase the risk profile. The vulnerability can disrupt mobile communications and IoT devices relying on these modems, potentially affecting service continuity. MediaTek has assigned Patch ID MOLY01519028 to address this issue, though patch deployment timelines may vary across device manufacturers.

For European organizations, the primary impact of CVE-2025-20659 is the potential for remote denial of service on devices using affected MediaTek modems. This can lead to temporary loss of connectivity in mobile phones, IoT devices, and embedded systems, disrupting business operations, especially in sectors dependent on continuous mobile communications such as logistics, healthcare, and critical infrastructure. Telecommunications providers may experience increased customer complaints and service degradation if rogue base stations are deployed by malicious actors. The vulnerability could be exploited in targeted attacks against high-value assets or to cause widespread disruption in areas with dense mobile device usage. Given the widespread adoption of MediaTek chipsets in budget and mid-range devices popular in Europe, the scope of affected endpoints is significant. However, the lack of confidentiality or integrity impact limits data breach risks. The ease of exploitation without user interaction increases the threat, especially in urban environments where rogue base stations can be covertly deployed.

1. Immediate deployment of the vendor-provided patch (MOLY01519028) across all affected devices and modems is critical. Coordinate with device manufacturers and mobile network operators to ensure timely updates. 2. Implement network-level detection and mitigation strategies to identify and block rogue base stations, including the use of radio frequency monitoring tools and anomaly detection systems. 3. Encourage users and administrators to update device firmware regularly and verify the authenticity of network connections. 4. For enterprise IoT deployments, segment networks to isolate vulnerable devices and limit exposure to untrusted wireless environments. 5. Collaborate with telecom providers to enhance base station authentication mechanisms and reduce the risk of rogue station exploitation. 6. Monitor network traffic for unusual patterns indicative of attempted exploitation or service disruption. 7. Educate security teams about this specific threat to improve incident response readiness. 8. Consider deploying endpoint detection solutions capable of identifying modem crashes or abnormal behavior related to this vulnerability.