CVE-2026-20458 Overview
CVE-2026-20458 is a memory corruption vulnerability in the MediaTek Modem component caused by a missing bounds check. An attacker operating a rogue base station can trigger the flaw when a User Equipment (UE) device connects to the malicious cell. Successful exploitation leads to remote escalation of privilege on the affected device without requiring additional execution privileges or user interaction. MediaTek tracks the issue as MSV-7298 and addresses it with patch MOLY01402160. The vulnerability is classified under CWE-787 (Out-of-bounds Write) and affects the modem's cellular protocol handling.
Critical Impact
Remote privilege escalation on affected devices with no user interaction required, exploitable by any attacker within radio range operating a rogue base station.
Affected Products
- MediaTek Modem firmware (patch MOLY01402160)
- User Equipment (UE) devices using vulnerable MediaTek modem baseband
- See MediaTek Security Bulletin - July 2026 for the full device list
Discovery Timeline
- 2026-07-01 - CVE-2026-20458 published to NVD
- 2026-07-02 - Last updated in NVD database
Technical Details for CVE-2026-20458
Vulnerability Analysis
The vulnerability resides in the MediaTek Modem firmware, which processes cellular protocol messages exchanged between the UE and the serving base station. A missing bounds check during message parsing allows attacker-controlled data to write beyond the intended buffer boundaries. This out-of-bounds write (CWE-787) corrupts adjacent memory structures inside the baseband processor.
Because the modem baseband executes with elevated privileges relative to the application processor, corruption in this component can lead to remote escalation of privilege. The attack requires only radio proximity to the target device, classifying the attack vector as adjacent network. No authentication, user interaction, or prior code execution on the device is needed.
Root Cause
The root cause is the absence of proper length or size validation on a field within a cellular protocol message handled by the modem firmware. When the modem processes a crafted message from the base station, it writes attacker-supplied bytes to a fixed-size buffer without verifying that the input length fits within the allocated region. This is a classic bounds check omission tracked as issue MSV-7298 by MediaTek.
Attack Vector
Exploitation requires the attacker to operate a rogue base station within radio range of the target device. Cellular UEs may attach to a rogue cell that advertises stronger signal or matching operator identifiers, particularly when downgrade or cell reselection conditions are met. Once the UE connects, the rogue base station transmits a crafted protocol message that triggers the out-of-bounds write inside the modem. The attack complexity is high because it depends on rogue cell setup and successful UE attachment, but no user action is required on the target device.
No public proof-of-concept or exploit code is available for CVE-2026-20458 at the time of publication. Refer to the MediaTek Security Bulletin - July 2026 for vendor-supplied technical detail.
Detection Methods for CVE-2026-20458
Indicators of Compromise
- Unexpected modem crashes, resets, or radio subsystem restarts on affected devices
- Devices attaching to unfamiliar cells with unusual PLMN or Cell ID values in areas where those networks should not exist
- Anomalous baseband log entries referencing malformed protocol messages during cell attach or reselection
Detection Strategies
- Monitor mobile device management (MDM) telemetry for abnormal modem reboot counts and firmware fault reports across the fleet
- Deploy rogue base station detection tooling on high-value devices to flag IMSI-catcher or fake cell activity
- Correlate baseband crash reports with location and cell attachment history to identify targeted radio attacks
Monitoring Recommendations
- Track firmware and patch level compliance against MediaTek Security Bulletin - July 2026 across all managed mobile endpoints
- Alert on devices reporting patch levels older than the fix containing MOLY01402160
- Log and review cellular attachment events in enterprise mobility management platforms for repeated attach failures or unusual cell handovers
How to Mitigate CVE-2026-20458
Immediate Actions Required
- Apply the vendor firmware update containing patch MOLY01402160 as soon as it is available from the device OEM
- Inventory all mobile devices using MediaTek basebands and confirm patch status against the July 2026 bulletin
- Prioritize patching for high-risk users likely to be targeted by rogue base station attacks, including executives and travelers
Patch Information
MediaTek has released patch MOLY01402160 addressing issue MSV-7298. Device OEMs must integrate this modem firmware update into their over-the-air (OTA) releases. Consult the MediaTek Security Bulletin - July 2026 and contact the device manufacturer for OEM-specific release timelines.
Workarounds
- Disable 2G or legacy radio access technologies on devices that support the option, reducing exposure to rogue base station downgrade attacks
- Enable carrier or OS-level rogue cell warnings where supported (for example, Android 2G disable and network notifications)
- Restrict use of unpatched devices to trusted radio environments until OEM firmware updates are deployed
# Example: Disable 2G on supported Android devices via ADB
adb shell settings put global preferred_network_mode 9
# Verify current patch level against MediaTek bulletin
adb shell getprop ro.build.version.security_patch
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
