CVE-2025-20708 Overview
CVE-2025-20708 is an out-of-bounds write vulnerability in the MediaTek modem firmware caused by an incorrect bounds check [CWE-787]. The flaw allows an attacker operating a rogue base station to trigger remote escalation of privilege against a connected user equipment (UE) device. No user interaction or additional execution privileges are required. MediaTek tracks the fix under Patch ID MOLY01123853 and Issue ID MSV-4131. The vulnerability affects more than 60 MediaTek chipset models spanning 4G LTE and 5G NR baseband processors used in smartphones, tablets, IoT modules, and automotive platforms.
Critical Impact
A rogue base station within radio range can write beyond allocated modem memory, gaining elevated execution context on the baseband without any user interaction.
Affected Products
- MediaTek 5G NR modem platforms: NR15, NR16, NR17, NR17R
- MediaTek smartphone SoCs including MT6833, MT6853, MT6877, MT6885, MT6893, MT6983, MT6985, MT6989, MT6991
- MediaTek automotive and IoT chipsets including MT2735, MT2737, MT8675, MT8771, MT8791, MT8797, MT8893
Discovery Timeline
- 2025-09-01 - CVE-2025-20708 published to NVD alongside the MediaTek September 2025 Product Security Bulletin
- 2026-02-17 - Last updated in NVD database
Technical Details for CVE-2025-20708
Vulnerability Analysis
The vulnerability resides in the MediaTek modem (baseband) software stack, which processes cellular protocol messages from the network. An incorrect bounds check fails to validate the length or offset of attacker-controlled data before writing it into a fixed-size buffer. The resulting out-of-bounds write corrupts adjacent modem memory, including control structures used by the baseband firmware.
Because the modem subsystem runs with elevated privileges relative to the application processor, memory corruption inside the modem grants the attacker an execution foothold below the operating system. Successful exploitation enables remote escalation of privilege, allowing the attacker to manipulate cellular signaling, intercept traffic, or pivot toward the application processor.
Root Cause
The defect is classified under [CWE-787] Out-of-Bounds Write. MediaTek's advisory attributes the issue to an incorrect bounds check in the modem code path that handles network-originated data. The check permits values that exceed the destination buffer capacity, so a crafted message size or field length triggers the overflow during processing.
Attack Vector
Exploitation requires adjacent network access. The attacker operates a rogue base station that transmits on the cellular bands supported by the victim device. Once the UE attaches to the rogue cell, the attacker sends malformed signaling messages that reach the vulnerable modem code path. No user interaction is needed, and the device does not need to be unlocked. The attack scope mirrors threat models previously demonstrated against baseband processors using software-defined radio platforms and open-source cellular stacks.
No public proof-of-concept code is available, and verified exploitation details have not been released. See the MediaTek Product Security Bulletin September 2025 for vendor technical details.
Detection Methods for CVE-2025-20708
Indicators of Compromise
- Unexpected modem firmware crashes, resets, or ramdump events logged by the cellular subsystem on affected MediaTek devices
- Repeated forced attachment to unfamiliar Cell IDs (CIDs), Tracking Area Codes (TACs), or PLMN identifiers inconsistent with the carrier footprint
- Sudden downgrade events from 5G NR to LTE or legacy radio access technologies in areas where 5G coverage is normally available
Detection Strategies
- Inspect mobile device management (MDM) telemetry and Android bugreport data for modem subsystem exceptions originating in baseband components corresponding to Patch ID MOLY01123853
- Correlate radio environment scans against trusted operator cell databases to identify rogue eNodeB or gNodeB transmitters operating in proximity to enterprise locations
- Monitor for anomalous IMSI catcher signatures, including suspicious reject causes, identity requests sent in cleartext, or repeated authentication failures
Monitoring Recommendations
- Enroll affected MediaTek devices in a mobile threat defense or unified endpoint management solution that reports firmware patch levels and modem build versions
- Track the MediaTek monthly security bulletin and downstream OEM (Original Equipment Manufacturer) advisories to confirm propagation of the September 2025 patch set
- Deploy cellular signal monitoring at sensitive sites to identify unauthorized base stations transmitting on licensed bands
How to Mitigate CVE-2025-20708
Immediate Actions Required
- Apply the MediaTek September 2025 security patch level on all affected devices once OEM firmware updates are released
- Inventory deployed MediaTek-based devices using the chipset list above and prioritize patching for handsets used by high-value users
- Restrict the use of vulnerable devices in high-risk physical environments where rogue base station attacks are plausible
Patch Information
MediaTek addressed the issue under Patch ID MOLY01123853 and Issue ID MSV-4131, documented in the MediaTek Product Security Bulletin September 2025. The fix is distributed to device OEMs, who must integrate it into their respective firmware images. End users receive the correction through an over-the-air (OTA) update from the device manufacturer or carrier.
Workarounds
- Disable 2G fallback where the platform supports it, reducing exposure to legacy rogue cell attacks while awaiting firmware updates
- Restrict roaming and configure preferred network type settings to limit unnecessary attachment to unverified cells
- For sensitive deployments, use Faraday enclosures or RF shielding to prevent radio attachment when the device is not in active use
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
