CVE-2026-20457: Modem Input Validation Flaw Enables Remote Denial of Service

Technical summary

CVE-2026-20457 is a null pointer dereference (CWE-476) in Modem's input validation logic. The vulnerability allows an attacker operating a rogue base station to send malformed messages that trigger an unhandled null pointer exception, causing a system crash. The attack vector is adjacent network (AV:A), indicating the attacker must be within radio range or control network infrastructure. Attack complexity is high (AC:H), suggesting specific conditions or configurations must be met. No authentication or user interaction is required. The impact is availability only; confidentiality and integrity are not affected.

Business impact

Service disruption affects mobile device availability and user productivity. For organizations managing cellular-connected IoT, automotive, or critical infrastructure devices, unexplained crashes caused by rogue base stations represent an availability risk. While the immediate impact is limited to the modem subsystem, repeated exploitation could degrade network reliability and user trust. The medium CVSS score reflects the localized nature of the impact, but the ease of exploitation (no privileges needed) warrants timely remediation.

Affected systems

The vulnerability affects Modem implementations. No specific vendor, product version, or device model details are provided in the official disclosure. Organizations should consult the patch ID (MOLY01826924) and issue ID (MSV-7301) with their device manufacturers and carriers to determine exposure in their deployed modem firmware versions.

Exploitability

Exploitation is straightforward for an attacker with the ability to operate or control a cellular base station. The attack requires no authentication, no user interaction, and no special execution privileges. However, the attacker must be within radio range (or have network infrastructure control), which limits opportunistic attacks to targeted scenarios. Attack complexity is rated high, suggesting the attacker may need to craft messages to specific modem variants or configurations, but this is a technical hurdle rather than a strong security control.

Remediation

Apply the vendor's patch referenced as MOLY01826924 (issue MSV-7301) as soon as it becomes available for your modem firmware. Coordinate with your device manufacturer and mobile carrier for availability and deployment timelines, particularly for embedded or IoT devices where firmware updates may require special processes. Until patched, consider minimizing exposure to untrusted or unfamiliar cellular networks, especially in sensitive operational contexts.

Patch guidance

Locate and apply patch ID MOLY01826924 via your device manufacturer's official update mechanism. Verify the patch availability against the vendor advisory to confirm applicability to your specific modem hardware and firmware version. Test the update in a non-critical environment first if your devices support staged rollouts. For managed fleet deployments, coordinate with your mobile carrier to ensure modem firmware updates are deployed alongside device OS patches. Document patch deployment for compliance and incident response readiness.

Detection guidance

Monitor for unexpected system reboots or modem crashes that correlate with location changes or base station connections, particularly in environments where rogue base station detection is not yet deployed. Advanced detection requires packet capture and analysis of radio-layer messages to identify malformed input that triggers the crash. Mobile security platforms and network monitoring tools should be configured to detect anomalous base station behavior or repeated connection failures to the same cell sites. Consider deploying rogue base station detection solutions (IMSI catchers) in high-security environments.

Why prioritize this

Although CVE-2026-20457 carries a medium CVSS score, it should be prioritized because exploitation requires no authentication or user interaction and is accessible to any attacker within radio range who controls a base station. The attack surface is inherent to cellular connectivity, making this relevant to all mobile-connected devices. The high attack complexity (AC:H) suggests patch verification testing may take time, but this should not delay remediation planning. Organizations with critical IoT or vehicular deployments should prioritize this higher than general enterprise mobile device fleets.

Risk score, explained

The CVSS 3.1 score of 5.3 (MEDIUM) reflects a denial-of-service impact with limited scope and no confidentiality or integrity risk. The adjacent network vector (AV:A) recognizes that the attacker must be within radio proximity or control network infrastructure, reducing the global attack surface compared to internet-facing vulnerabilities. The high attack complexity (AC:H) acknowledges that successful exploitation may require specific modem configurations or firmware variants. However, the lack of authentication (PR:N) and user interaction (UI:N) requirements elevate the risk beyond a low-severity flaw. Organizations should interpret this score as 'act reasonably soon' rather than 'critical emergency.'

Frequently asked questions