CVE-2026-20431: Modem Logic Error DoS Vulnerability

CVE-2026-20431 Overview

CVE-2026-20431 is a remote denial of service vulnerability affecting MediaTek Modem components. The vulnerability stems from a logic error in the modem firmware that can cause a system crash when a User Equipment (UE) connects to a rogue base station controlled by an attacker. This vulnerability requires no user interaction and no additional execution privileges for exploitation, making it particularly concerning for mobile device security.

Critical Impact

Attackers controlling a rogue base station within adjacent network range can remotely crash affected devices without any user interaction, disrupting mobile connectivity and device availability.

Affected Products

• MediaTek Modem firmware (specific versions identified in Patch ID: MOLY01106496)
• Devices utilizing MediaTek modem chipsets
• Issue tracked as MSV-4467

Discovery Timeline

• April 7, 2026 - CVE-2026-20431 published to NVD
• April 7, 2026 - Last updated in NVD database

Technical Details for CVE-2026-20431

Vulnerability Analysis

This vulnerability is classified under CWE-770 (Allocation of Resources Without Limits or Throttling). The flaw exists within the MediaTek modem component and manifests as a logic error that fails to properly handle certain conditions when a device connects to a base station. When exploited, this logic error triggers a system crash, resulting in a complete denial of service condition.

The attack requires the adversary to be within adjacent network range and operate a rogue base station. Once a vulnerable device connects to the malicious base station, the attacker can trigger the logic error remotely. The vulnerability does not require authentication or user interaction, making exploitation straightforward for attackers with the necessary infrastructure.

Root Cause

The root cause is a logic error in the MediaTek Modem firmware's base station connection handling routine. The modem fails to properly validate or process certain conditions during the connection sequence, leading to resource allocation issues that culminate in a system crash. The lack of proper bounds checking or state validation allows the crash condition to be triggered remotely.

Attack Vector

The attack vector requires adjacent network proximity, meaning the attacker must be within radio range to establish a rogue base station. The attack flow proceeds as follows:

1. The attacker deploys a rogue base station within proximity of target devices
2. Vulnerable UE (User Equipment) devices scan for and connect to available base stations
3. The rogue base station sends crafted signaling that triggers the logic error
4. The modem component crashes, causing a system-wide denial of service
5. No user interaction or special privileges are required on the victim device

The vulnerability exploits the trust relationship between mobile devices and base stations, leveraging the modem's insufficient validation of connection parameters or signaling data.

Detection Methods for CVE-2026-20431

Indicators of Compromise

• Unexpected device reboots or system crashes when in specific geographic locations
• Modem crash logs or kernel panic messages referencing MediaTek modem components
• Multiple devices experiencing simultaneous connectivity issues in the same area
• System logs indicating abnormal base station connection behavior

Detection Strategies

• Monitor device telemetry for patterns of modem-related crashes across device fleets
• Implement network monitoring to detect unauthorized or suspicious base stations in enterprise environments
• Deploy mobile threat detection solutions capable of identifying anomalous cellular behavior
• Review system crash dumps for signatures matching modem component failures

Monitoring Recommendations

• Enable verbose logging on mobile device management (MDM) platforms to capture crash events
• Establish baseline metrics for device stability and alert on deviations
• Coordinate with mobile carriers for suspicious base station activity in critical operational areas
• Implement SentinelOne Mobile Threat Defense for real-time anomaly detection

How to Mitigate CVE-2026-20431

Immediate Actions Required

• Apply the MediaTek security patch identified by Patch ID MOLY01106496 as soon as it becomes available from device manufacturers
• Check with device OEMs for firmware updates addressing MSV-4467
• Prioritize patching for devices used in sensitive or high-risk environments
• Consider restricting device usage in areas where rogue base station attacks are likely

Patch Information

MediaTek has released a security patch addressing this vulnerability. The patch is tracked as Patch ID MOLY01106496 and Issue ID MSV-4467. Detailed information is available in the MediaTek Security Bulletin April 2026. Device manufacturers will need to integrate this patch into their firmware updates, so end users should monitor for OEM security updates.

Workarounds

• Enable airplane mode when in untrusted or high-risk locations until patches are applied
• Utilize Wi-Fi calling as an alternative to cellular connectivity in sensitive environments
• Deploy enterprise mobile security solutions that can detect anomalous network behavior
• Limit exposure by avoiding use of affected devices in areas susceptible to rogue base station deployment