CVE-2025-20631: Mediatek SDK Privilege Escalation Flaw

CVE-2025-20631 Overview

CVE-2025-20631 is an out-of-bounds write vulnerability in the MediaTek wireless LAN access point (WLAN AP) driver. The flaw results from an incorrect bounds check that permits writing outside allocated memory. A local attacker with low privileges can exploit this weakness to escalate privileges without user interaction. MediaTek addressed the issue under Patch ID WCNCR00397141 and Issue ID MSV-2187, disclosed in the MediaTek Product Security Bulletin for February 2025. The vulnerability affects multiple MediaTek Wi-Fi chipsets widely deployed in consumer and enterprise access points and routers, including the MT7615, MT7622, MT7663, MT7915, MT7916, MT7981, and MT7986.

Critical Impact
Local attackers can achieve privilege escalation on devices running vulnerable MediaTek WLAN AP driver code, gaining high impact on confidentiality, integrity, and availability without user interaction.

Affected Products

MediaTek Software Development Kit
MediaTek MT7615, MT7622, MT7663 Wi-Fi chipsets
MediaTek MT7915, MT7916, MT7981, MT7986 Wi-Fi chipsets

Discovery Timeline

2025-02-03 - CVE-2025-20631 published to NVD alongside MediaTek's February 2025 Product Security Bulletin
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-20631

Vulnerability Analysis

The vulnerability lives in the MediaTek WLAN AP driver, the kernel-space component that manages access point functionality on MediaTek Wi-Fi silicon. An incorrect bounds check in the driver allows a caller to write past the end of an allocated buffer. This maps to [CWE-787: Out-of-bounds Write], a memory corruption class frequently used to overwrite adjacent kernel structures.

Exploitation requires local access with low privileges but no user interaction. Successful exploitation grants the attacker elevated privileges on the target device, which on affected router and access point platforms typically means full root control of the network device.

Root Cause

The driver performs a bounds check that fails to correctly validate the size or offset of data written into a buffer. When the check is bypassed with attacker-influenced input, the driver writes attacker-controlled bytes beyond the buffer boundary. In kernel context, that overflow can corrupt adjacent objects, function pointers, or task credentials to hijack execution or elevate the calling process.

Attack Vector

The attack vector is local. An attacker with existing low-privileged access to the device sends crafted input to the WLAN AP driver interface, typically through an ioctl, netlink, or configuration control path exposed by the driver. Because the WLAN AP driver runs in kernel space, a successful out-of-bounds write yields kernel-level code execution and privilege escalation.

MediaTek has not published exploitation details, and no public proof-of-concept or exploit code is available at this time. See the MediaTek Security Bulletin February 2025 for vendor-authoritative technical scope.

Detection Methods for CVE-2025-20631

Indicators of Compromise

Unexpected kernel oops, panic, or driver crash entries in device system logs referencing WLAN AP driver modules
New or unexpected processes running with elevated privileges on MediaTek-based access points or routers
Unauthorized modifications to firmware, configuration files, or persistence hooks on the network device

Detection Strategies

Inventory network infrastructure and identify devices running MediaTek chipsets (MT7615, MT7622, MT7663, MT7915, MT7916, MT7981, MT7986) and confirm firmware patch status against MediaTek's February 2025 bulletin
Monitor syslog and remote logging feeds from access points for kernel warnings, driver faults, or repeated wireless subsystem restarts
Correlate management-plane authentication events with subsequent configuration or firmware changes to spot post-exploitation activity

Monitoring Recommendations

Forward access point and router logs to a centralized SIEM or data lake for long-term retention and correlation
Alert on anomalous administrative sessions, unexpected SSH or shell activity, and configuration drift on wireless infrastructure
Track outbound connections from network devices to detect command-and-control activity following a successful privilege escalation

How to Mitigate CVE-2025-20631

Immediate Actions Required

Apply firmware updates from device vendors that incorporate MediaTek Patch ID WCNCR00397141 for the affected chipsets
Restrict local and management access to affected access points and routers to trusted administrators and networks only
Audit accounts and services on affected devices to remove unnecessary local access that could be leveraged for exploitation

Patch Information

MediaTek released the fix under Patch ID WCNCR00397141 (Issue ID MSV-2187) as part of the February 2025 Product Security Bulletin. Downstream OEMs consuming the MediaTek SDK must integrate the patch into their firmware builds and publish updates to end users. Consult the MediaTek Product Security Bulletin February 2025 and the specific device vendor's advisories for firmware availability.

Workarounds

Segment wireless management interfaces onto dedicated administrative VLANs and block local shell or SSH access from user networks
Disable unused WLAN AP driver features and management services where operationally feasible until firmware updates are applied
Enforce strong authentication and rotate credentials on affected devices to reduce the pool of accounts an attacker could abuse for local access

bash

# Configuration example: restrict management access to a trusted subnet
iptables -A INPUT -i br-lan -p tcp --dport 22 -s 10.0.0.0/24 -j ACCEPT
iptables -A INPUT -i br-lan -p tcp --dport 22 -j DROP
iptables -A INPUT -i br-lan -p tcp --dport 443 -s 10.0.0.0/24 -j ACCEPT
iptables -A INPUT -i br-lan -p tcp --dport 443 -j DROP