CVE-2025-20646: Mediatek SDK Privilege Escalation Flaw

CVE-2025-20646 Overview

CVE-2025-20646 is a critical out-of-bounds write vulnerability discovered in MediaTek's WLAN Access Point firmware. The vulnerability exists due to improper input validation in the wlan AP FW component, which could allow an attacker to achieve remote privilege escalation without requiring any user interaction or additional execution privileges.

This firmware-level vulnerability affects multiple MediaTek chipsets commonly deployed in wireless networking equipment, routers, and IoT devices. The exploitation does not require authentication, making it particularly dangerous for devices exposed to untrusted networks.

Critical Impact

Remote attackers can exploit this out-of-bounds write vulnerability to escalate privileges on affected MediaTek wireless devices without user interaction, potentially gaining full control over network infrastructure.

Affected Products

• MediaTek Software Development Kit (SDK)
• MediaTek MT6890
• MediaTek MT7915
• MediaTek MT7916
• MediaTek MT7981
• MediaTek MT7986

Discovery Timeline

• 2025-03-03 - CVE-2025-20646 published to NVD
• 2025-04-22 - Last updated in NVD database

Technical Details for CVE-2025-20646

Vulnerability Analysis

This vulnerability is classified as CWE-787 (Out-of-Bounds Write), a memory corruption issue that occurs when the WLAN AP firmware writes data past the boundaries of allocated memory buffers. The root cause stems from insufficient validation of input data before processing, allowing malformed or oversized input to corrupt adjacent memory regions.

The network-accessible nature of this vulnerability significantly increases its risk profile. An attacker positioned on the same network—or remotely if the device is internet-facing—can send specially crafted packets to trigger the out-of-bounds write condition. Successful exploitation grants the attacker elevated privileges on the affected device without requiring any form of authentication or user interaction.

Root Cause

The vulnerability originates from improper input validation within the WLAN AP firmware processing routines. When the firmware receives network packets, it fails to adequately verify the size and boundaries of incoming data before writing it to memory buffers. This absence of proper bounds checking allows an attacker to craft malicious input that exceeds expected buffer sizes, resulting in memory corruption.

The specific issue, tracked internally by MediaTek as Patch ID WCNCR00389074 and Issue ID MSV-1803, indicates a known boundary validation deficiency in the wireless network processing code path.

Attack Vector

The attack vector for CVE-2025-20646 is network-based, requiring no authentication or user interaction. An attacker can exploit this vulnerability by:

1. Identifying a vulnerable MediaTek-based wireless device on the network
2. Crafting malicious network packets designed to trigger the input validation flaw
3. Sending the crafted packets to the target device's WLAN AP firmware
4. Exploiting the out-of-bounds write to corrupt memory and escalate privileges

The attack complexity is low, as the exploitation path does not require specialized conditions or complex timing. Once the out-of-bounds write is triggered, the attacker can potentially execute arbitrary code with elevated privileges, compromising the confidentiality, integrity, and availability of the affected system.

Detection Methods for CVE-2025-20646

Indicators of Compromise

• Unusual network traffic patterns targeting wireless access points, particularly malformed or oversized packets
• Unexpected firmware crashes or restarts on MediaTek-based wireless devices
• Anomalous process behavior or privilege changes on affected devices
• Network devices exhibiting signs of unauthorized configuration changes

Detection Strategies

• Deploy network intrusion detection systems (IDS) to monitor for abnormal traffic targeting MediaTek wireless devices
• Implement firmware integrity monitoring to detect unauthorized modifications
• Configure logging on network devices to capture and alert on suspicious wireless management traffic
• Conduct regular vulnerability scans to identify unpatched MediaTek devices in your environment

Monitoring Recommendations

• Monitor network segments containing MediaTek wireless infrastructure for suspicious packet activity
• Enable enhanced logging on routers and access points running affected MediaTek chipsets
• Establish baseline network behavior for wireless management traffic and alert on deviations
• Integrate device logs with SIEM solutions for centralized analysis and correlation

How to Mitigate CVE-2025-20646

Immediate Actions Required

• Identify all devices in your environment using affected MediaTek chipsets (MT6890, MT7915, MT7916, MT7981, MT7986)
• Apply the latest firmware updates from device manufacturers that incorporate MediaTek's security patch
• Isolate vulnerable devices that cannot be immediately patched from untrusted network segments
• Review and restrict network access to wireless management interfaces

Patch Information

MediaTek has released security patches addressing this vulnerability as documented in their March 2025 Security Bulletin. The fix is identified by Patch ID WCNCR00389074. Device manufacturers integrating MediaTek chipsets should incorporate this patch into their firmware updates, and end users should apply the latest available firmware from their device vendors.

Contact your device manufacturer to obtain firmware updates that include the MediaTek security patches. The patch addresses the improper input validation issue by implementing proper bounds checking before memory write operations.

Workarounds

• Segment vulnerable wireless devices behind firewalls with strict access control lists
• Disable remote management interfaces on affected devices until patches can be applied
• Implement network-level filtering to restrict traffic to vulnerable devices from untrusted sources
• Consider deploying additional network monitoring to detect exploitation attempts