CVE-2026-20422 is a vulnerability classified under CWE-617 (Reachable Assertion) found in multiple MediaTek modem chipsets including MT2735 through MT8893 series. The flaw arises from improper input validation within the modem firmware, which can trigger an assertion failure leading to a system crash. This crash results in a denial of service condition affecting the modem’s operation. Exploitation requires an attacker to operate a rogue base station that a user equipment (UE) connects to, enabling the attacker to send crafted inputs that trigger the assertion. No additional privileges or user interaction are necessary, making the attack vector relatively straightforward once the attacker controls the network environment. The affected modem versions are NR15, NR16, NR17, and NR17R, which are widely deployed in mobile devices and potentially embedded telecommunications equipment. The CVSS v3.1 base score is 6.5, indicating a medium severity, with an attack vector of adjacent network (AV:A), low attack complexity (AC:L), no privileges required (PR:N), no user interaction (UI:N), unchanged scope (S:U), no impact on confidentiality or integrity (C:N, I:N), but high impact on availability (A:H). Although no exploits have been reported in the wild, the vulnerability poses a risk of remote denial of service, potentially disrupting communications. MediaTek has assigned a patch ID (MOLY00827332) and issue ID (MSV-5919), indicating a fix is available or forthcoming. The vulnerability is significant for devices relying on these chipsets, especially in environments where rogue base stations could be deployed, such as public spaces or targeted attacks.

For European organizations, this vulnerability could lead to service disruptions in mobile communications and IoT devices using affected MediaTek modems. Telecommunications providers, mobile network operators, and enterprises relying on cellular connectivity for critical operations may experience degraded service availability or outages. The remote denial of service could be exploited in targeted attacks using rogue base stations, potentially impacting user devices, embedded systems, and network equipment. This may affect sectors such as finance, healthcare, transportation, and public safety that depend on reliable mobile connectivity. Additionally, the presence of rogue base stations is a known threat vector in urban and high-value areas, increasing the risk of exploitation. While confidentiality and integrity are not directly impacted, the loss of availability can disrupt business continuity and emergency communications. The broad range of affected modem versions suggests a wide footprint, increasing the potential scale of impact across European markets.

1. Apply the official MediaTek patch identified by Patch ID MOLY00827332 as soon as it becomes available to ensure the vulnerability is remediated at the firmware level. 2. Implement network monitoring solutions capable of detecting rogue base stations or suspicious cellular network behavior to prevent devices from connecting to attacker-controlled infrastructure. 3. Employ mobile device management (MDM) policies to enforce firmware updates and restrict connections to trusted networks where feasible. 4. Educate users and administrators about the risks of connecting to unknown or unsecured cellular networks, especially in sensitive or high-risk environments. 5. Collaborate with mobile network operators to enhance detection and mitigation of rogue base stations within their networks. 6. For critical infrastructure, consider deploying multi-factor communication channels or fallback mechanisms to maintain availability if cellular connectivity is disrupted. 7. Conduct regular security assessments and penetration testing focused on cellular network security to identify potential exploitation paths. 8. Maintain an inventory of devices using affected MediaTek chipsets to prioritize patching and monitoring efforts.