CVE-2025-20634 Overview
CVE-2025-20634 is a critical out-of-bounds write vulnerability (CWE-787) affecting MediaTek modem firmware across a wide range of chipsets. The vulnerability exists within the modem component and stems from a missing bounds check, which could allow remote code execution when a user equipment (UE) device connects to a rogue base station controlled by an attacker. No user interaction is required for exploitation, making this a particularly dangerous vulnerability for mobile devices and IoT hardware utilizing affected MediaTek chipsets.
Critical Impact
Remote code execution is possible without user interaction when a device connects to a malicious base station, potentially compromising mobile devices and IoT systems at the firmware level.
Affected Products
- MediaTek NR16, NR17, NR17R (5G NR Modem Software)
- MediaTek MT6800 series (MT6813, MT6835, MT6835T, MT6878, MT6878M, MT6879, MT6886)
- MediaTek MT6895 series (MT6895, MT6895TT, MT6896, MT6897, MT6899)
- MediaTek MT6980 series (MT6980, MT6980D, MT6983, MT6983T, MT6985, MT6985T)
- MediaTek MT6989 series (MT6989, MT6989T, MT6990, MT6991)
- MediaTek MT8000 series (MT8673, MT8676, MT8678, MT8795T, MT8798, MT8863)
- MediaTek MT2737
Discovery Timeline
- February 2025 - MediaTek releases security patch (Patch ID: MOLY01289384)
- 2025-02-03 - CVE-2025-20634 published to NVD
- 2026-02-17 - Last updated in NVD database
Technical Details for CVE-2025-20634
Vulnerability Analysis
This vulnerability is an out-of-bounds write condition in MediaTek's modem firmware. The flaw occurs when the modem processes certain data without proper bounds checking, allowing an attacker to write data beyond the intended buffer boundaries. Since the modem operates at a low level within the device architecture, successful exploitation could grant an attacker significant control over the affected device's communications and potentially the entire system.
The attack requires the victim's device to connect to a rogue base station (fake cell tower) controlled by the attacker. Once connected, the attacker can send specially crafted data that triggers the out-of-bounds write condition, leading to arbitrary code execution within the modem's execution context. Notably, no additional execution privileges are required beyond establishing the malicious connection, and no user interaction is needed to trigger the vulnerability.
Root Cause
The root cause is a missing bounds check in the modem firmware's data processing routines. When handling certain types of network communications data, the firmware fails to validate that the data length falls within expected boundaries before writing to memory buffers. This oversight allows maliciously crafted data to overflow the intended buffer and overwrite adjacent memory regions, potentially corrupting critical data structures or injecting executable code.
Attack Vector
The attack vector is network-based, requiring the attacker to operate a rogue base station (also known as an IMSI catcher or fake cell tower). When a vulnerable device enters the range of this malicious base station and connects to it, the attacker can exploit the vulnerability by sending specially crafted network protocol messages that trigger the out-of-bounds write.
The exploitation process involves setting up a rogue base station that mimics legitimate cellular infrastructure. When a vulnerable device connects (which can occur automatically without user awareness), the attacker transmits malformed modem protocol data. The missing bounds check in the modem firmware allows this data to overwrite memory beyond the intended buffer, ultimately achieving remote code execution on the device's modem processor.
Detection Methods for CVE-2025-20634
Indicators of Compromise
- Unexpected modem crashes or restarts that may indicate exploitation attempts against the firmware
- Connections to unknown or suspicious base stations that could represent rogue cell tower attacks
- Anomalous cellular network behavior or unexpected data transmissions from affected devices
- System instability or unexpected behavior following cellular network connectivity events
Detection Strategies
- Monitor for devices connecting to unregistered or suspicious base stations through cellular network monitoring solutions
- Implement firmware integrity checking mechanisms to detect modifications to modem components
- Deploy endpoint detection and response (EDR) solutions capable of monitoring low-level system behavior on mobile and IoT devices
- Utilize network anomaly detection to identify unusual cellular protocol traffic patterns
Monitoring Recommendations
- Maintain an inventory of all devices using affected MediaTek chipsets within your organization
- Implement centralized logging for mobile device management (MDM) solutions to track device connectivity events
- Monitor MediaTek security bulletins for additional updates and indicators related to this vulnerability
- Consider cellular network security solutions that can detect rogue base station attacks
How to Mitigate CVE-2025-20634
Immediate Actions Required
- Apply the firmware update containing Patch ID MOLY01289384 from MediaTek or your device manufacturer immediately
- Contact device manufacturers (OEMs) for updated firmware releases that incorporate the MediaTek security patch
- Identify and inventory all devices in your environment using affected MediaTek chipsets
- Implement network segmentation to limit potential lateral movement from compromised mobile/IoT devices
Patch Information
MediaTek has released a security patch addressing this vulnerability, identified as Patch ID MOLY01289384 (Issue ID: MSV-2436). The patch details are available in the MediaTek Security Bulletin for February 2025. Organizations should work with their device manufacturers (OEMs) to obtain firmware updates that incorporate this patch, as MediaTek provides patches to OEMs who then distribute them through their own update mechanisms.
Workarounds
- Avoid connecting devices to untrusted or unknown cellular networks when possible
- Implement cellular network security measures to detect and block rogue base station attacks
- Consider disabling automatic network selection features where operationally feasible
- Deploy MDM policies to restrict connectivity to approved carrier networks only
- For high-security environments, consider RF shielding or controlled cellular environments until patches can be applied
# Verify MediaTek firmware version on Android devices (requires root or ADB access)
# Check for modem firmware version containing the MOLY01289384 patch
adb shell getprop gsm.version.baseband
adb shell cat /sys/devices/virtual/mtk-modem/modem_info/version
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
