CVE-2026-20500: MediaTek MT2716 Firmware DoS Vulnerability

CVE-2026-20500 Overview

CVE-2026-20500 is an improper input validation vulnerability in the MediaTek Modem component. The flaw allows a local attacker with user-level execution privileges to trigger a system crash, resulting in a denial of service condition. Exploitation requires user interaction on the affected device.

MediaTek has assigned Patch ID MOLY01810811 and internal Issue ID MSV-9232 to track the fix. The vulnerability affects a wide range of MediaTek chipsets used in smartphones, tablets, and other devices with cellular modem capabilities.

Critical Impact
Successful exploitation crashes the modem subsystem, disrupting cellular connectivity and device availability across dozens of MediaTek chipset families deployed in mobile and embedded devices.

Affected Products

MediaTek smartphone chipsets: MT6835, MT6858, MT6878, MT6881, MT6897, MT6899, MT6982VB, MT6986, MT6988, MT6991, MT6993
MediaTek tablet and compute chipsets: MT8668, MT8676, MT8678, MT8755, MT8775, MT8792, MT8793, MT8863, MT8873, MT8883
MediaTek automotive/IoT chipset: MT2716

Discovery Timeline

2026-09-07 - CVE-2026-20500 published to the National Vulnerability Database (NVD)
2026-09-07 - MediaTek publishes the September 2026 Product Security Bulletin
2026-09-09 - Last updated in the NVD database

Technical Details for CVE-2026-20500

Vulnerability Analysis

The vulnerability resides in the Modem component of MediaTek's baseband firmware. The affected code path fails to properly validate input before processing, allowing malformed data to reach logic that cannot safely handle it. When triggered, the modem subsystem enters an unrecoverable state and crashes.

The attack requires local access with user execution privileges and depends on user interaction to reach the vulnerable code path. The impact is limited to availability. Confidentiality and integrity of device data are not affected. Successful exploitation disrupts cellular services, including voice, SMS, and mobile data, until the modem or device is restarted.

The vulnerability is categorized under CWE-295 Improper Certificate Validation in the NVD entry, although the description points more directly to a general improper input validation weakness in the modem parser.

Root Cause

The root cause is missing or insufficient input validation on data processed by the modem firmware. A specific field or structure is not bounds-checked or type-checked before being consumed by downstream logic. Malformed input drives the modem into an invalid state, producing a crash rather than a graceful error rejection.

Attack Vector

A local, authenticated attacker with an unprivileged user account triggers the flaw by delivering crafted input to the modem interface, typically through an application or utility that interacts with baseband services. User interaction, such as opening a malicious application or accepting a prompt, is required for the exploit to reach the vulnerable code path. Remote or network-based exploitation is not indicated by the advisory.

No public proof-of-concept exploit code has been released for CVE-2026-20500. Technical details are described in prose only. Refer to the MediaTek Product Security Bulletin - September 2026 for vendor-provided context.

Detection Methods for CVE-2026-20500

Indicators of Compromise

Unexpected modem subsystem crashes or resets recorded in device logs, particularly modem_ssr or baseband ramdump events on Android devices using affected MediaTek chipsets.
Repeated loss of cellular signal, SIM registration failures, or radio interface layer (RIL) reinitialization events shortly after launching or interacting with a specific application.
Presence of applications requesting unusual telephony or modem-adjacent permissions on affected devices.

Detection Strategies

Aggregate mobile device logs (logcat, tombstones, kernel panics) into a centralized log platform and alert on abnormal frequencies of modem restart events.
Correlate modem crash timestamps with application install, launch, and permission grant events to identify likely trigger applications.
Track MediaTek chipset inventory across your mobile fleet to prioritize monitoring on devices matching the affected chipset list.

Monitoring Recommendations

Monitor mobile device management (MDM) telemetry for repeated cellular connectivity failures on devices with affected MediaTek chipsets.
Ingest mobile endpoint and MDM logs into your SIEM or data lake and build detections for repeated baseband subsystem failures.
Track patch adoption rates across the fleet against vendor OTA release schedules to identify unpatched devices.

How to Mitigate CVE-2026-20500

Immediate Actions Required

Inventory mobile and embedded devices in your environment that use the listed MediaTek chipsets, using MDM data or asset management tools.
Prioritize deployment of vendor firmware updates that include MediaTek Patch ID MOLY01810811 once released by device OEMs.
Restrict installation of untrusted applications on affected devices, since exploitation requires local user interaction with a malicious app.

Patch Information

MediaTek addressed CVE-2026-20500 in Patch ID MOLY01810811, tracked internally as Issue ID MSV-9232, and published the fix in the MediaTek Product Security Bulletin - September 2026. The patch must be integrated by device OEMs and delivered through vendor over-the-air (OTA) updates. Contact your device manufacturer or carrier for firmware availability on specific device models.

Workarounds

Limit application installation to vetted sources such as official app stores with active malware scanning.
Apply MDM policies that block sideloading and enforce application allowlists on managed mobile devices.
Educate users to avoid installing applications from untrusted sources and to report unexpected loss of cellular service.

bash

# Example: use adb to check MediaTek chipset and baseband firmware version on an Android device
adb shell getprop ro.hardware
adb shell getprop ro.board.platform
adb shell getprop gsm.version.baseband